1995 Chevy 454 P30 overheating

Thanks guys you all the thoughts. This is a MH we bought strictly to rent it out, so I need to get this right. It comes back Sunday from a 4 day rental and I am going to take the time to get it right before it goes out again! I will start with a complete flush and pressure test, then to the thermostat and finally to the water pump, it is debris free even behind the condenser. So I should come to a conclusion soon. I will post back as to my outcome and/or progress on the way.
Again thanks so much for the input, it is really appreciated!