Before you decide that the distributor is the culprit, do some more digging.
A symptom of the timing being too far advanced is pinging (a death rattle in the engine when accelerating)
A symptom of the timing being too far retarded is overheating.....
Before spending a lot on a new distributor that may - or may not - fix the problem, borrow or buy a timing light and measure the timing.
Block the vacuum advance hose to the carb. Measure at idle, 1500, 2000, 2500, 300, 3500, 4000rpm.
Let us know what you find.
Investigation is generally cheaper than throwing money at an issue and hoping for it to be a fix.
Other causes of overheating:
buggered clutch fan
fan too small / not enough blades
no shroud
small radiator
blocked radiator
head gaskets on backwards
too lean
etc etc....