a 4g63 is a very interesting option, and like most cars it can be done, but it would probably cost a good ammount if someone hasn't already built a direct swap kit, personally I would stick with a gm drivetrain, I know a 4.3 could be decently built and still bolt to any tranny a small block can if saving weight (or shifting it back anyhow) is a goal, but I tend to agree with the lsx guys, very tough motors, just drop one in and spray your way to your goal.