Which Torsion Bar?

1.03" or bigger. With a 400 up front I wouldn't even hesitate with a set of 1.06" bars from Firm Feel. I have 1.12" bars on my Duster, and it has a 340, manual steering, no A/C, aluminum radiator, intake, headers, etc. Still has iron heads, but that's about it. But my car is set up pretty stiff for the street, a little more autoX based than most. Of course, I also still drive it as my primary vehicle, if that means anything to you.

I'd also be looking to do something else for front tires, at least going up to a 225/60/15 if you're going to stay with 15" rims.