Why? Why would you put a crappy motor in a good car? It's way too much work just to fit that in there in the first place. Stick with the 4.6. That, and if the 572 is going for cheap, I would imagine it is either stolen, or it has so many issues (like all chevies... tee hee) that it isn't worth building. The 4.6 (presumably) has more than enough snot to get the job done.