If I had to do it all over again it would be LS, with a turbo and a power glide in a fox chassis ford...probably not a mustang since they are done to death, but a fairmont or thunderbird (they look cooler anyways).

I have also toyed with the idea of doing a sbm or gen 3 hemi into an old RX7 or 240SX. A guy local here has on old RX7 with a mild LS and T56, runs 10.40s wheels up every pass.