I don't know the OHV engine, but if it runs hot* and the radiator and water pump are fine, then you may have blockages in the waterways inside the block and head, common if the engine has been run with plain water instead of coolant with an anti-corrosion additive.
Running hot in itself can cause problems as components have to work at temperatures they're not designed for.
(* presuming you've checked that it actually is running hot, not that you also have a temp sensor or gauge problem).
This is one of the water fittings from my Sportshatch engine (OHC, and actually the fitting for the pipe that runs under the twin carburettors) showing how they can get. (For those who know the car and the state it was in, this wasn't from the car itself, it's a pair I bought separately, so not just this bad because the car was this bad generally).