Wow! Which engine do you have? Did you have the valves redone when you did the head gaskets?
If its is his 95 its the OHV. There is one here that is over 500K, original everything. Owner took great care, coolant changes, etc.
Manual trans though. OHVs weakness at very high miles is the lower intake gasket, more rare head gaskets, and sometimes the head, it can crack, but it is a relatively minor repair that can be done in a day. Everything else on that engine may outlast the driver!