Since the caps in the differential hold bearing races, it's not as critical as an engine bearing cap holding separate bearing shells. When they are bolted down, there should be no step at the parting line and inside diameter should be slightly smaller than the bearing race outer diameter. All the ones I have pulled over the years were never marked, I doubt the older ones were marked either. If the cap bolts down tight and holds the race tight with out cracking, you are probably safe to continue. Look close at the surface finish where it was honed, the housing and cap should have a continuous finish all around, it very unlikely a different cab will have the same finish on the inside, use a magnifier to really get a close look. Same where they bolt down, look for staining on both the housing and cap.
