What rear end is in your stock 1987 Chevy 34 ton truck?

There's no such thing as a "1987 Chevy 34 ton truck". Chevrolet didn't produce a 34-ton truck in 1987 (or any year). That weight class is far beyond what Chevrolet's heavy-duty truck lines offered. 34 tons is the territory of specialized heavy equipment, not commercial trucks from major manufacturers like Chevrolet.