I think that in many production RWD cars the extra electric fan is mainly for the AC. At least, in my 1980's M-B cars it only comes on from the AC refrigerant temp switch. You could also wire one to come on from automatic tranny fluid temp if using an add-on cooler. The after-market ones are fairly wimpy, but would help for above.
To really help, people like the Ford 2 spd fans from the 90's (Taurus, Crown Vic?). Much info on the H.A.M.B. hot rodder site.
