Mach im in the same boat as, i have an 88 GT no mass air, but i have a cobra intake along with a 70mm TB. 65mm would be the right choice for a stock engine, but im not keeping it stock for too much longer, thats why i went with 70mm. Im still running 19lb "stock" injectors. i was concerned about this, wondering if i should go to bigger injectors. Ive done some research and found that the 19 lbers are sufficient enough