904 internals

I wouldn't waste my money on red clutches and Kolene steels.

5 clutches in a 4 clutch front drum (thin clutches)...I use stock replacement raybestos clutches and re-tumbled stock steels
TCS multi spring kit
Tranzact trans brake valve body (if yours is really a race car, forget about that trans-go crap and get a real valve body)
Lever is dependent on your valve body- get whichever the valve body recommends. I have a 5.0 in mine.
Relocate the vent to the back of the case
4 pinion steel planetary for the front atleast...you'll strip out the aluminum there in no time if you don't swap it out.

I have had my trans apart a good handful of times this season with this above setup...everything looked mint

This was in a 3535lb car going 11.20's off a trans brake and LOTS of street miles

If you need help getting the right parts, give Hutch at Hutch Transmissions a call...He'll set you up right and doesn't mark up his prices like alot of the other popular vendors do for these transmissions