A few water spots on the cylinders? Not a big deal.
The steel shim gaskets were .020 thick. The composites are double that. Most motorhome engines were in the 7.5 compression ratio range. Adding a thicker gasket will only worsen your squeeze. Consider milling the heads .040 and using a steel shim gasket again. This will put you closer to 8.0 to 1. Still not that great, but without replacing pistons, you are limited. If you are really only interested in a cruiser, forget any type of single plane intake. They need RPM to make any power. Same with the gas sucking double pumper carb. A standard Edelbrock performer (NOT Performer RPM) with a 440 spec ThermoQuad will make more power with better mileage. Definitely use headers with a good 2 1/2" dual exhaust system.
I have a motorhome 440 in my '74 Dodge truck. I had the heads milled .050 but left the 58,000 mile bottom end alone: Its factory stock EXCEPT: I overcammed it with a MP 284/484 stick. I was trying to save a few coins and I already HAD the cam and lifters. the motor would probably be faster with a stock 440 magnum cam, since they were designed for an rpm range of 1500-5000. The stock heads begin to choke at 4500 .... right where the 284 cam is supposed to be in its power band. Its a classic mismatch of components. I want to swap in the stock cam when funds allow it. If you are truly looking for advice, MINE is to stay conservative on the cam and induction with a low compression mill.