dont know what to tell ya. mine has that same probem. i have new radiator, heater core, water pump, hoses, thermosat, inlet is good, replaced foam inside the ducts, adjused cables, tried with and without fresh air boot, ran weaker coolant mixture, ran richer coolant mixture...... vent temps are 90F. with a poorly insulated cab its just enough to **** you off yet keep you from freezing to death. my 71 that had more problems than i could ever imagine was COOKING! at the vents. i would put the fan on low and have to shut it off it was so hot. most vehicles are at least 140F. my little ranger bakes my butt at 160F