Or do a 6spd swap and run 4th low. Get a CR turbo if your gonna run work stock and a RedLine box or p-pump it if rules allow. A 6.7 VGT turbo would work great if the rules allow you to ditch the electronic controler on the 6.7 turbo and make your own manual controler using springs and WG actuator or an air cylinder, but some may cry about it and say that you have modified a stock turbo.