To keep the engine cool you need to follow the design of the German engineers of the beetle by separating the cool air side of the engine from the hot air side. I fabricated a floor and side walls for my engine compartment out of sheet metal and made sure all the engine cooling tin was installed.
Also make sure that fresh air can enter the cool air side. My car has an actual spare tire so there is a large opening under it to the engine compartment.
The oil temperature gauge has never read more than just over 180 degrees.