You asked for input from 4 speed racers, not sure if one has replied yet, I see a lot of speculation. Here's my 2 cents from 20 years behind a 4 speed. My setup was a street/strip 340, metallic clutch disc, running mid 11's in street trim, high 10's on a small spray kit. Car would hook solid. I broke anything that would break in the 8 3/4, axle, spider gears and the last straw was when I broke the ring gear after a test session before a street race. Upgraded to a Dana 60 with a spool. Problem solved. I'm sure others can respond with problems they had with there 23 spline but mine never gave me a bit of trouble. The only upgrade I did was steel shift forks, the brass tend to brake with hard shifting use. I'm not out to argue with anyone, you asked so I'm sharing my experience.
