I have a Tremec TKO in my car behind its supercharged 377 stroker, and have not broke it yet to date. I may have hurt a syncro or something while running it at the NMRA finals in September, but I am not sure yet. It may just be the clutch adjustment. Regardless, it's been behind the mill for a few years and before that behind the previous 550 HP 302 combo. It has done well over all. I still haven't really run the trans behind the big boost set-up at the track (on slicks) though. So, that could change everything. But, yes... a T56 is still much stronger than a TKO.
For those who are not aware, however... Tremec is suppose to come out with a new "bullet proof" or race duty transmission. Supposedly it's supposed to come out this spring, although I wouldn't bet on it until the fall. If anyone is interested in a TKO, T56, or possible info on the upcoming Tremec I would contact
D&D Performance.