I think there are a couple of steps first before a rebuild.
`.1. How old is the oil? have you changed it in the last 20 years?
2. At zero, the engine will sound like a box of metal marbles in a metal garbage can.
If neither of the above, first change your oil and filter, go 20/50, see if the gage pumps up.
After that use another gage . again only if 1 and 2 have been done.
If the new one is just as low, then its rebuild time. Your car is 45 years young.
GTJOEY1314
