I have a 1972 MONTE CARLO ...the heads were done and i can't see any leaks in the rad or hoses but the rad...?

level runs at about 6 inches down, when i fill it , it runs out the overflow when at operating temp...they say it will find its own level, but 6 inches, is this normal in a 1972 350 chev?...runs at 195-200 degrees.