"Vin5563"......There's a company called Source Engineering. They make a replacement engine fan for the Monaco rear radiator coaches. I'm not sure if they go back as far as your year model, but it adds/returns about 40 HP to your coach. The engine fan on yours could propel a small airplane. Source Engineering redesigned the fan to be more aerodynamic, yet it still cools as efficiently as yours. They're about $600.00. Most can be changed from the bedroom access cover.
I added one to my 400 ISL and could feel seat of the pants acceleration. On mine, it only added 25 HP. The smaller the engine, the faster it spins and the more HP you save by changing to their fan.
If you can chip yours (transmission capable of more HP) and add the fan, you'll be pleasantly surprised.
Don & Mary
2019 Newmar Dutch Star 4018 - All Electric
2019 Ford Raptor Crew Cab