[Pyrotechnic]

Not surprising. The 4 and 6 cyl early T5's can be used behind a V8 with the right clutch disk, but they are weak and the output shaft is small. A V8 T5 from an F-Body will be stronger but with lots of power and heavy truck they still aren't that strong.

The only other car transmission that's stronger is a 6 speed T56. You can also have a T5 strengthened to handle lots of power. Either way, a strong manual overdrive transmission is not a cheap affair. You can step down to a Muncie or Super T10 4 speed and they will be strong and reasonably priced, but they won't have the overdrive.