torsion bar adjustment
Where might one find these factory specs and measurements?
Factory Service Manual or a Chiltons if you must. The '70 Chiltons I have is actually pretty good. Once you see a Chrysler, dodge or Plymouth service book from that era, You'll probably want one. Occasionally a local library will have them - the automotive collection at the Philadelphia library is amazing (assuming they didn't get rid of it to save money..)
1968 Plymouth
Height, Valiant 2.125" Barracuda 1.375" plus minus .125
Camber, most negative recommended, 1/4* left, zero right (This was for high crowned roads that were the norm, if your roads are flairly flat, then both sides can be the same. As tyres developed they tend to prefer more negative camber. You may find a '72 service book shows more negative. I don't have anything that new. If you want to spec 1/4* negative, see how that works out. I tend to run at least 1/4* negative camber.
Caster: power steering 1.125* positve.
Toe In: 3/32" - 5/32" (on a stock dia. tire) go for the 3/32" or equiv in degrees.