Having rebuilt a half dozen and taken apart about a dozen plus water pumps 66 up type. The shaft and bearing are one piece. There really is no way to test without installing. Even with a good bearing, I have found the shaft pits under the seal collar and getting the mechanical seal to not leak around that pitting is the issue. So new bearing/shaft and seal. Impellers, fan mount are available also. The whole exercise is save the period correct housing.