I have a couple of options for you but unless your flatbed truck is using a B&W Turnover ball system the only way to connect your trailer to your gooseneck hitch is to use the Convert-A-Ball Cushioned 5th-Wheel-to-Gooseneck Adapter item # CAB-C5G.
The Convert-A-Ball has a 20,000 lbs capacity and attaches directly to your 5th wheel trailer's kingpin. I have linked an installation video below.
Another option would be to change the pin box on your CrossRoads Sunset Trail Reserve to a gooseneck... view full answer...
The Furrion Chill HE RV Air Conditioner System - Single Zone - 15,000 Btu - White # FR55PV will work great in your RV that has an opening for a second AC. This comes with everything needed to install and control through an included roof vent with a wall thermostat. view full answer...