1994 Toyota 4Runner 22re overheats at 60mph and above

Try replacing the thermostat again, if that doesn't fix the problem do the following below: Have it block and pressure tested-do the block first to pinpoint a combustion leaking into the cooling system or a gas analyzer to sniff for hydrocarbons at the radiator fill neck. Pressure test: do not do a pressure test if there's leakage at the head gasket this might cause coolant to leak into the cylinders and lock it up or bend a connecting rod if cranked thereafter. The head gasket should be repaired before doing the pressure test. If the block and pressure test passes check the following: thermostat, pressure test the radiator cap, clogged radiator, fan clutch, fan relay, radiator electrical fan, collapsed hoses, water pump.