The Tremec TR-3550 five-speed transmission is a good option for an upgrade from the T-5. The latest version of this transmission is Ford part number M-7003-R58 and costs $1,495. This transmission became known as the TKO when heavier input and output shafts were added. It's rated to handle 360 lb-ft. If you're stepping up from a T-5 to a Tremec, you'll need another bellhousing because the Tremec and T-5 transmission mounting patterns are different. We might add that we know people who can break a TKO running 14s, while another fellow is successfully running high 11s with a T-5 pass after pass. How you drive the car and use the gearbox will have a lot of effect on longevity.