Assuming you have a good trans, with proper clearances and some of the shift overlap problems addressed......Some guys never get this far.......then you move on to whats going to break. First is usually the alum planet. Rings the center out. So you upgrade to the steel pinion planet. After this, it's usually the output shaft and then finally the input. So at this point you have $1100 worth of shafts in the trans, along with your $400 steel planets. Assuming you had a nice trans before, with alum drums etc, you are approaching big bucks in a factory cased trans.

My car was 3200lbs, 10.5 tire, 446" motor with a single fogger. Never had bigger than a .040 jet in it. It would 60ft in the high 1 teens. I had everybody in the world work on the trans and it had GOOD parts. It was out for SOMETHING every other race. Broken hard parts, smoked clutches.....something. I put the glide in it and it would go the season no problem. Plus was faster