no thermostat is your overheating problem, and one that "works" doesn't mean one the correct capacity for the engine/truck - start over, make it all right and let us know what the problems are then! you could start at a wrecking yard, find a correct original rad, if it's not good, get it rebuilt, put the correct fan on and put a thermostat in - if it still overheats we'll help ya figure out what's wrong w/ the engine
Bill
