Can an LS1 throttle body be used on an LS6 intake for a Chevrolet Corvette C5?

Yes, you can absolutely use your LS1 throttle body on an LS6 intake manifold. In fact, the factory LS1 and LS6 throttle bodies are completely identical ⁸. They share the same 3-bolt pattern and bore size, so your existing LS1 throttle body will bolt directly to the LS6 intake without any adapters, and there is no performance benefit to buying a factory LS6 throttle body to replace it ⁹.

Since you're likely doing an LS6 intake swap on your C5, keep in mind that if you are putting this manifold on a 1997–2000 LS1, you will need to either swap out your factory coolant crossover lines or carefully chisel/grind flat the plastic ribs on the underside of the LS6 manifold so it can sit flush over your existing coolant tubes ⁹.

Difficulty: Easy

I don't have a verified torque figure for the throttle body bolts on your car, so don't take a number from me on it — check the factory service manual. The procedure itself is straightforward: clean the mating surface, install a fresh rubber gasket if the old one is flattened or brittle, start all three fasteners by hand, and then tighten them evenly in a couple of passes so you don't warp the throttle body housing or strip the threaded brass inserts in the manifold.