Should I regear my high-mileage stock 10-bolt or save for a stronger rear end?

First, find out which 10-bolt you have:

GM 10-bolt	Stock capacity (Speedway)	Notes
8.5 / 8.6	The only high-performance 10-bolt; can hold about 1,000 hp built properly	Large square lugs at 5 and 7 o'clock; flat webs on the front; 28- or 30-spline
8.2 (1964–72)	About 400 hp on street tires, 350 on drag radials, 300 on slicks	Built for racing: about 500 hp on street tires, 400–450 on slicks
7.5 / 7.625	About 350 hp on street tires	Maxes out around 500 hp with maximum effort and expense; 28-spline only, no 30-spline upgrade

Telling them apart: measure from the lower center cover bolt to its neighbors — about 3-1/4 in on a 7.5, 3-3/4 in on an 8.5/8.6. The 8.5 has large square lugs at 5 and 7 o'clock; the 7.5's are small. Confirm with the codes stamped on the axle tube.

Regearing notes: 10-bolt carriers are gear-specific (2- or 3-series). The 3-series is preferred for numerically higher performance gears. Speedway warns that a stock carrier in a 7.5 or 8.2 isn't strong enough for high performance or off-roading. If it's a 7.5 behind a modified LS, the money may be better spent on a stronger rear.