I doubt that your underhood temp comes close to that seen on many of the current automibiles.These modern Honda and Toyota and 454 powered motor homes of a few years ago have me shaking my head.
Rubber things underhood of the modern stuff has a hard life.
I really think you have a good working package there.
That 400 will give some grunt down low but may be a little thirsty.An AIR COOLED transmission cooler is a necessity for lower cooling system loads and better transmission life and make sure the ignition timing is not retarded as that can increase operating temperatures of the exhaust.
