We're getting off topic here. Maybe a new thread would be good. I will post a parts list and the mods I did and why in the transmission drivetrain forum.
Grumpy, Maniacmechanic, what part of your 700r4s did you break?
I know the GM 5 pinion sets are all gone. Fortunately, TCI has stepped up and is producing a nice set now. About the same price as GM.
Dana at Probuilt is the best person to talk to about making one survive in a drag race application.
In my experience, the 3-4 clutch is the weak link. The Smart tech is one solid way to address this. Getting the 2-3 shift timing just right is critical. I started in my first build running the Superior 2nd servo. The apply release ratio is too hard to tune around. It tends to cause a 2-3 bind that kills the 3-4 clutch. I switched to the Sonnax 2nd and also run the Sonnax 4th servo. I installed a TH400 front servo return spring on the 2nd servo for a clean release every time.
Behind the 3-4 clutch, the ne,t weakest point is probably the sun shell. The beast or the smart shell both cure this.
I have a modified Transgo 2-3 kit in the valve body with several mods of my own. Lots of Sonnax stuff.