I've seen a few posts about the motor mounts and what not when swapping big blocks, 6.2, etc. Found some interesting stuff (to me at least) while looking at my '85-88 parts catalog for the frame question, thought some might be interested. The engine "support" (piece that typically ends up under the harmonic balancer) is different based on engine. 292 and 454 have their own specific pieces, while the small block V8 and 6.2L share the same one. The actual rubber motor mounts are the same for 292/5/5.7, but different than the 454, while the 6.2L has it's own. . The motor mount stuff is pretty common knowledge I'm sure, but the front crossmember isn't so much I guess.