Have you tried running the heater full blast while it's over heating? Does that help cool it down or does it even blowing hot air? That can give you a hint at what the problem might be.
'64 Sport Fury, 528 Hemi, FiTech EFI, 4-speed, 4.10 Dana 60 '57 Belvedere 2dr sedan, current project in process '19 Cherokee Trail Hawk Elite '03 Ram 2500 CTD HO, 6-speed 214,000 miles and still going strong
