If they are used for trim or panels, I usually replace them with stainless. Looks smarter and easier to get them apart.
If they are structural (brakes, steering, suspension, drivetrain etc) I either replace with OE, or clean and reuse.
Much of the ones used in these types of applications are fairly specialised anyway.
Usually the threads are OK it is mainly the aesthetics of the heads, in which case toss them in the sand blaster and epoxy them after they have been fitted.
You could even re-plate them, but it probably isn't worth the effort/cost unless it is a concours restoration.