Okay I need to replace my driveshaft, and also need to shorten it for my new 8.5". I am estimating only about 400hp out of the motor, and I have a 700r-4 with some work done to it behind the motor. Lastly 3.73's and posi in the rear with street tires, but will be throwing E/T street drag radials on track days. I would like opinions on what size driveshaft I should go with. Also is it worth it to upgrade to aluminum? I am not looking to piss money away but I am not looking to penny pinch on it either. Any help is greatly appreciated and don't hesitate to ask if you want more info.