The T5z is the best transmission for retrofits of 4 speed or automatics in classic cars and hotrods with a small block. Extremely versatile and usable in street usage under 450 horsepower.
The Super Duty T5 is a step up from the T5's used in the 1985-93 Mustangs. The gear sets in the earlier t5's were built with a 3.35 first gear with a .68 overdrive. The Super Duty T5 is built with a 2.95 first and a .63 overdrive for a more fuel efficient experience as well as more torque handling then its former counterparts. This transmission is built specifically for the aftermarket and is sold through the TREMEC dealer network, as well as, Ford Racing.
For more information read "The many different faces of the T-5."