Did dash air repair alter engine cooling design

I would be more concerned that the AC will not work well with the added heat from the engine radiators if I read your post correctly. Most diesel PU trucks have three cooling items in series... AC condenser, Charge air cooler, and the engine radiator. An extra set of fins is not going to decrease the air flow enough to affect the engine cooling. My OEM AC condenser is in front of my engine radiators adding heat to them, not behind them.