gm t-5's with no mods, but t-5's from a v8. It makes a difference. The v8 t-5 has the fine tooth front input shaft. 21 or 23 tooth I believe. The v6 t-5 has the course input shaft around 10 teeth.
I have run both world class and non-world class t-5's with the same results.
just don't shock the transmission with a hard hit, like dropping the clutch with no load on the the transmission.
To reduce shock, I do the following at the drag strip. I use a line lock on the brakes, and rev the engine to 5000 rpms, and slightly let out the clutch to preload the driveline, then let the brake line lock off and let go of the clutch on the last yellow light on the tree