If your car is a strip car, don't worry too much about leakage. It usually starts when you run C-clips on the street. The seals are'nt designed to handle the loads of daily driving with lots of cornering.
With that light weight of a car, 31 spline will last forever. You can stick with the 4 lug if you want. There are plenty of cars with more HP and running quicker times than you.
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