radiator sounds old and too small, i would upgrade to a decent rad make sure u have a shroud and put a 180 therm in dont use that mr gasket high flow crap i had a 2 month old one overheat my new 331 stroker cause it would not open at any temp. Get a 180 stant and drill a couple 1/8 inch holes in the flange for a little extra protection just incase it wont open u still have a little coolant flow into the engine, a 160 therm only means it opens and flows coolant into engine at 160 instead of 180 that wont change the final temp car running at. My car runs around 200 in traffic in the summer and i have a 180 therm. no overheating running great