Invest in a modern day mechanical temp guage. Compare it's readings to what the stocker guage says. My guage ('59) is at 3/4 scale when water boils....these things have'nt been calibrated in 40+ years so do yourself and your pv a favor and get an up to date calibration via a new unit. Velcro a new mech. guage underneath the dash and check it out against the stocker. If it really is overheating i'd check the thermostat or a lower hose colapse........let us know what you find!