Parts - Block and pistons
With new rings, provided the bores measure up within tolerance, then it is a good idea to clean out the piston rng grooves carefully and also cross-hatch-hone the bores to facilitate bedding-in of the rings without undue heat build-up.
Withn 500 miles of steadily increasing time-at-power and plenty of short-term load to build engine pressures and force the rings into good contact with the walls early on, the engine should be capable of sustaining full power for a few minutes. Within that period a good idea to make one oil & filter change, circa 100 ~ 200 miles. However, there are no hard and fast rules... e.g. hold this or that power or revs for so long etc.
A brand new short engine will generally 'feel' a lot tighter for a lot longer than a rebuilt one.