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Going through some of my old pix of the work I have done on two BJ pans I think I have some pix that I took during their builds might help others. Most have been posted but not together.
These pix are close to about as basic as you can get but the front of the pan shown here is has a couple of additions... for the front suspension mostly.

The VW pan is a tunnel unibody design. Unlike other unibody designs the body is bolted on to the pan to complete the unibody function. The tunnel is made from an upper formed piece that goes from just in forward of the beam mount to the end where the transmission mount ends. The lower part of the tunnel matches the length of the upper tunnel front to rear.
Implanted between the two halves in the rear is the torsion tube which is welded in place while the two halves of the tunnel are spot welded together. If you are going to be rough with what you are using the pan for then I would recommend welding the seams together to back up the spot welds.
The torsion tube has end supports that attach to the floors to help limit the potential twisting of the tunnel. The top photo shows the mounting on the top of the crosspiece of the floors and shows the lower hook. The bottom shows the lower hook which is known to break off under hard use.
This shows the frontal addition for the mounting of the front beam.
The bottom of the pan showing the "beading" (forming) that helps the limiting of the twisting loading on the basic tunnel as well is the floors of the tunnel. Notice the "beading" of the lower part of the mounting of the front suspension which, again, helps stop some of the potential twisting of the front beam. Depending on your use of the pan additional support might be needed.
I will add some more info later.

Lee

Very nice lee

IRS trailing arm pivot mount.
The two pix show that the threaded part of the mount is probably a pressed in/interference fit way of doing thing and it part of the upper tunnel piece before the two tunnel pieces are spot welded together.

For what it is worth.

Lee

One of the things I should have mentioned is that the two halves are spot welded together not seam welded. This means that the seams could be made stronger, especially the trans mount area, by seam welding them.

Lee

As I already posted the VW bug's front beam went from a King and Link setup to a Ball-joint the in '68 here in the "states" VW went from a swing axle to an Independent Rear-end Setup (IRS). Sometime in '71 as I remember the bug went from a double spring plate to a single spring plate. Because of what I think are other changes in the single vs. the double spring plate setup the connection fastener pattern was changed also so they single and double couldn't be interchanged (an old engineering trick)
On the left is the double spring plate 4 bolt setup with the trailing arm mount between the tow spring plates. The trailing arm mount on the right is the newer single spring plate with three holes.
This is the later single spring plate and trailing arm shown sans the fasteners.
This shows the trailing arm's suspension stop on the torsion housing. In this case the trailing arm itself is notched to allow more suspension travel downwards. In this case the suspension has some weight on it so you can see what happens when the suspension drops and the amount of travel here is longer at the stub axles.
This shows the notch with no weight on the suspension. There are two ways to make the notch: one where the notch matches the suspension notch with some gap at both ends to be sure that there is no dragging/wear on either the stop or the spring plate.

The other way is to make the forward cut on the spring plate then continue a line back to the radius of the spring plate.

Be sure in both cases to put radiuses in the notch to get rid of the potential of failure due to the square corner.
There are a couple of ways to do this but this way is the safest. Do not reach under the spring plate or crawl under when you are either preloading or un-preloading as if there is a problem with things coming apart it is too quick for anyone to even see it. Hands, fingers, arm or heads can be broken in fractions of a second.
Some of the tools used. I did a post years ago but the phots are now part of photobucket and not of good quality. The tool show has extra washers added as well as a nut that does the work. The handled nut that comes with the tool I used under the nut to stop any walking back off of the adjusting nut can do. The two washers make the clamping easier but make the backing off easier too.
This is the preload angle before clamping back up and sliding the spring plate back into the torsion housing and back onto the stop. Before you start raising the spring plate up make sure it is very close but not under the stop on the torsion housing so the amount of side movement is negligible for safety sake.

The stock angle is 19° to 20° and this is set at ~26° for riding in the sand.

Lee

Also remember that the inside splines of the torsion bar and the outside splines of the torsion bar are off-set so going back or forth on the two sets of spline adjustment can be finer than just one set of splines.

Lee

This shows the frame head and it's bolt inserts that mount to the body for additional support. In glass body buggies and some Baja bugs the mounting from the body to the beam mount these bolt locations on the "bobbing of the body" are often removed or do not exist. The fiberglass itself usually isn't that strong to take the loading that can happen.
The loss of the connection to the body can allow the beam to twist in these directions.
One of the ways to off-set this problem is the commercially available upper and lower beam supports. The upper supports connect to the front firewall above what is often referred to as "the Napoleon's hat" because of it's shape while the lower tube connects to the two (per side) bolts that go from the underside of the pan into the body.

The bars also might be good to have in-case of a not too violent collision.

lee

Been fighting with the mockup on my black dune buggy and supporting the front beam.
This is the commercial upper front beam support that goes from the firewall to clamp on the front beam; there is a lower one also. If you have a copy of Baja Bugs & Buggies by Jeff Hibbard go to the third section, say page 55 and on and there is some talk about supporting the end of the front beam. He states that the supports are added to keep the outer ends of the beam from being bent which is true.

Dustymohave and I were talking about this and, if possible, a diagonal between the two supports should be added as long as the steering goodies aren't going to hit things.

What he doesn't talk about is the front mount on the pan that the beam is bolted to. If you have a Baja where the nose of the Baja is not bolted to the beam mount or a glass buggy which normally does not connect to the pan any farther than the front Napoleon's hat area the mounting area can be twisted or bent (this info was from a ACVW junkyard owner may nears ago). I still am fighting on what to do but one of the statements made was that maybe you might not need the upper beam support as long as you are more careful, don't jump the buggy, watch out for hidden "Whoops" and watch for others that aren't watching out for others.

The other things on the supports for the beam is protecting the beam and mount from twisting. The bend angle on the upper supports is still low but it should give some additional support. Both my buggies (as I remember as the one buggy is not here) as the pans front beam mount both have taken a slight twist to it.

The book is old but it is still a good thing to have as there is still a lot of important things talked about in it.

Lee