after seeing the pic of your radiator/fan combination, i would look into a fan setup from a late model ?? that would incorporate a shroud covering the whole core. also, most factory fan setups are a two speed, having the high speed kick on whenever the ac is requested. i think that would go a long way toward easing your mind about the 80-90*temp/ac use issue. although the aftermarket fan manufacturers claim great things about their products, i'm not a "fan" of them [pun intended ], preferring factory setups instead. you may also consider a separate transmission cooler [with fan] to eliminate that heat source from contributing to the issue.