One thing you could look into is the 160 deg T-Stat. Too low of t-stat could make you run hotter because it is not letting the coolant stay in the rediator lon enought to cool it down.

I had a 77 vette that had a 160 deg t-stat in it and it ran 210-230 deg. Lost coolant all of the time. Put in a 180 deg t-stat and it ran 185-190 all of the time.

Just a thought,