Does anyone know how much in /out play is acceptable on the stub axles of a 1970 big block rearend.Mine, has .019 on one side and .023 on the other.

I beleive .001 to .010 smaller the better.What year car do you have, mid to late 70s GM had hardness problem with the inner stub shaft. I removed my wifes 78 and found c-clips laying in the botton of the diff. the shaft wore all the way through the clip grooves. Yet 2 garages told me the end play was fine.

The smaller the better. I don't know the specs on the C3's but a standard GM rear is .060, sixty thousands. Your's is probably okay. You need at least .001, it can't be tight.