Matt, if I were in your shoes, I would go with a T-5 transmission with the .70~ overdrive gear, and keep the stock rear end gears. The T-5 with the extra shifts will keep the engine in its optimum power band more often than a factory 4 speed which you start in 2nd gear (1st is granny gear for pulling stumps).
The stock rear end gears, even with the .70~ overdrive, will keep you from going faster than the stock brakes can stop you, while allowing you to keep up with highway traffic (excluding Mr Milliman, of course).
Carl
