Yes on the 318.
Small block early A headers are EXPENSIVE!! Like $1K a set.
Your 904 wont fit a small block.
The 727 will require floorplan mods to fit in an early A.
Cannot keep push buttons with that trans either.
Will need a different driveshaft.
Can keep the 7.25 rear end.
At least until it explodes....
Easiest path would be the 318 with a cable shift 904 (to keep the pushbuttons) and then you would not need a driveshaft.
Thank You for responding.
Thank You for this information, I am trying to follow everyone who responded, but a man can get pretty confused in here...lol
And look for a set of early A 273 exhaust manifolds and motor mounts.
That's the cheapest route.