MS type 4 in a fastback Type 3

[Piledriver]

The stock tb works fine with a lot of off the shelf TPS... IIRC I made an extension for mine using some 1/4" rod, pulled original flush shaft, cut a notch in it, put a matching tang on the 1/4" rod and a flat...worked fine.
IIRC I ended up using a Vanagon TB which was 50mm. IIRC had the right shaft and came with a switch or two.
It bolts on, same design, although you may want to open up the plenum inlet a bit.

Understand the tps is only needed for accel shot and idle logic. It is not a show stopper, or shouldnt be.
A simple switch for logic and using the MAP only for accel works just fine...
(tried it once for awhile when a tps died on me)