You wouldn't be the first to do it. You would need a double sump oil pan for a chevy motor which are made, maby some custom motor mounts which wouldn't be that big of a deal. If you have a T5, you would need a bell housing and input shaft from a older F-body with a T5.
I never have scene why there is this whole stupid ford vs chevy thing. So what, Ford built a better body and the SBC can't be beat.
4 bolt SBC blocks are all over the place. Alot stronger than a SBF 351 block, unless it's and R/Sportsman/aftermarket block which will cost 10 fold more. 400 cranks are all over the place, make a 383 for cheap.