Well I'm certainly no expert, but near as I can tell, not much difference - nothing that would not allow them to directly interchange. The 1/2" flywheel bolts are preferred (older versions used 7/16" bolts). Later heads have ports for smog, but can be simply plugged for your purpose.
You might want to also check Craiglist etc. locally for one on the cheap - I picked up a complete running used 292 nearby for $300 and am using it to mockup the swap into my '48.
sb