[Jack21]

As near as I can tell, the Tremec is a Mexican truck transmission that by design or happenstance fits a Ford toploader bellhousing, which fits a Ford engine. Somewhere along the line, they were being marketed as replacements for abused T-5's.

They work, but they'd work better with a gearset more suited to a Cobra, or a Mustang with 3.55 or 3.73 gears for that matter.
Thought if we Ford guys started griping, Tremec might listen. Doesn't even have to be Tremec per se', just an aftermarket gearset manufacturer (like Richmond) to grind a decent set of replacement cogs for the trans.

Toploaders are available from several sources completely refurbished, and about the same price as new T-5's. I wanted a good cruise gear for the car.

Richmond 5 speeds are good units, and with a big block, likely a good option.

The Tremec is in the middle price range. The T-5 is about $1100 - $1200 new. The Tremec, about $1300 (3550)- 1600 (TKO) new. Richmond around $1900 new.