Bill,
Couple of questions for you... When you say "overheats", does the radiator cap open up and let off pressure? Or, are you just watching the temp gauge? (You might want to buy a mechanical temp gauge and re-check.) Stock radiator, 7lb cap? Since it sounds like you've got the bodywork off, are you running a fan? Are you sure the thermostat is not up-side-down? What about your exhaust system, stock? If so, is the heat riser opening when the engine warms up? How many times have you fired up you new engine? Also, have you re-adjusted the valves?
Keep us posted,
