Hmm, I dunno about that... the only difference between a 232 and 258 is the crank.
Shaft vs. rocker is a model/year issue, 199, 232, 258 all got the same heads in a given model year. Originally shaft, then moved to rockers, then back to shaft around 72? pending the result of some lawsuit regarding rocker design, then ball-socket individual rockers up through the end.
Externally, all of the ports are absolutely identical up to the 4.0 heads. Last weekend I put '83 manifolds on a 70 head, and I checked -- ports match. It lined up fine to the cleaned-up 64 head on my bench.
Even the 1990 4.0 EFI manifold will BOLT ON to the 64 head. That's the RENIX head. 91 up fits up til they revised the head and raised the ports and made them smaller (hi flow heads). And THOSE heads still bolt onto all motors back to 1964 (introduction). (AMC and Chrysler switched from 7/16 to 1/2 headbolts, so some combos you need adapter washers (available aftermarket) and some need the head holes drilled.
There were different deck heights in various years, but I think (VERIFY THIS! DONT TAKE MY WORD!!) the hydraulic lifters will compensate, I don't know if there's different length pushrods.
The AMC six is a very versatile platform for motor hackery. The 258 is like a small V8 unless you need to build to rev over 6000 for extended periods.
It's a long motor, due to the 7 main bearings. But there's a lot of adapters available due to it's use in Jeeps, so you can put pretty much ant transmission behind it, AMC, GM, Ford, Chrysler. ANd they're cheap and plentiful!
