3.8SC wouldnt take the abuse unless you put some money into it. Go with a 302 ~250hp would be easy and cheap to get with E7TE heads and a mild cam, 5.0 headers. Use a carb with a duraspark blue module and distributer. Keep it floored the whole time. Thats how guys are making it over here with low hp cars. They stay cool and are still easy on fuel.
Remove the rear sway bar. Im hearing from guys that race late square body impalas doing that keeps the inside tire on the ground also keeps the car from spinning out. Hard to believe, but it works.
Run a slightly narrower rim on the outboard side. Will give you a little bit taller tire on the outside canting the car inboard and you can use the same tire size. Depending on what the restrictions are of course.
Not sure what to set the alignment to. Someone else would have to chime in.