Lots of people will tell you that you need a 4.25

I ran a 3.94 with the stock height tires, and the 3.67 with the short 13s. The only outlier is Blackhawk - I prefer the 3.94 with short tires there, and the 3.67 with short tires everywhere else.

My advice - don't invest in a 4.x final drive. Invest in races and seat time, and use stock 3.94 final drives with 14" wheels.