Check for a worn out timing chain, could cause cam and ignition to run retarded, causing an overheating problem. Easy to check, with distributor cap off, put a socket on the crankshaft bolt, rotate it around to "0" timing mark. Watch or have helper watch distributor rotor as you rotate crankshaft back, stop when it (the rotor) just starts to move, how many degrees did crankshaft move before rotor moved, the fewer, the better.
