You don't see 383 A bodies in FAST, either, and their exhaust manifolds are pretty readily available. And a 383 can be stroked to at least 470 or so cubes, so size isn't the problem. But like the 440 A bodies, the 383 A bodies have to run a factory carb, and the OEM AVS on an A body 383 flows maybe 550 cfms, which is too small for a stroker big block.
