You'll have to find someone REALLY "old-school" for this.
But it CAN be done right.
In the early 80s, when drag-racers were snapping up fox-body Mustangs for their light weight instead of performance (puh-leaze, the 1979-1982 Mustangs only outran the Mustang II by .2 seconds in the 1/4) a number of them went to Chevy Small-blocks for power.
Your best bet would be to find someone who's done that before.
Also, a Powerglide or a manual-
tranny would be easiest to install in such a swap, as they're easily adapted to more situations than other Chevy trannies, and MUCH easier to adapt than most of Ford's.
Of course, a good Lentech AOD would work, they do them with special bellhousings to put behind small-block Chevys, I ordered one from them for a side-project of mine.