The crank ends are machined to fit in the w body application. The front accessories are also slimmer than typical Ls engines to provide clearance. As far as mods goes if you don"t mind getting rid of D.O.D then you can basicly mod it just like a Ls engine, heads, cam, certain intake manifolds and other mods. You could also overbore the cylinders to get 5.7 displacement since the 5.3 and 5.7 have the same stroke. You will be limited however by header design due to the fwd layout. I say do it, it will be a fun project to do.