Those are stock rockerarm/shaft assemblies as used on all `65-up Type I engines. `61-`64 were similar but used different stands and 1:1 rockers vs 1.1:1. Pre`61 rested directly into cradles in the head casting but otherwise were also of similar design.
When VW guys talk about "solid" rocker shafts they're referring to ones which have been modified (or purpose-built) so as to do away with the spring clips and wavy washers. The shafts are drilled & tapped for bolts in the ends, and selective-thickness shims and spacers are used to set the individual rocker sideplays to ~.004". This stabilizes the valvetrain for high RPM and eliminates failures due to broken clips or wavy washers.
"Solid" shaft kit:
If the sparkplug insert is steel and grey or black in color, it's most likely the "K-D" style offered at your F.L.A.P.S. If copper colored or aluminum, it's a "Time Sert".
Time Serts have the same thread pitch on the inside & outside, allowing them to be thinner than the K-Ds which have a coarse, crude outside thread. Time Serts are also manufactured with the last thread or so not fully formed - after screwing them in you use a broaching tool to finish-size the thread and expand the insert out to lock it into the head. Properly installed, they're the best repair option short of welding. If you've got one that's backed out, odds are it's a K-D (they're infamous for that). Get a couple of new ones and plan on replacing along with that plug, at least until the head threads wear out to the point that a larger-O.D. insert is needed to keep the head in service. ½" length will work but a little of the insert ends up hanging into the chamber, allowing carbon build-up, so try to find 12mm or 7/16".
http://shop.advanceautoparts.com/p/kd-t ... 22988146-P
The Time Sert kit is kinda spendy to purchase for occasional use. Some places will rent the kit out, though (but it's of no use once a head's been reamed out to the larger size of the K-D insert).
http://www.mechanicstoolsandbits.com/ti ... 21_54.html
More often than not, if the plug threads needed repair the head is cracked - but it may still have years of service left provided you can get a plug to stay in the hole
