It appears to me that you have a hitch weight (1200) and a trailer GVWR (9450). With those weights, any 1 ton (SRW or DRW) would tow that rig just fine. A question to ask of yourself is if your tow vehicle will be used exclusively for towing? or will it be used as a daily commuter? My truck is a daily driver so I bought a 2013 RAM 3500 Crew cab 6.5' bed SRW. Now I'm guessing you bought a Montana 3400RL as that's the quickest 5th wheel Montana I can find in the size range you specified. It appears that it has a scalloped front end so that a slider wouldn't totally be necessary except in the most extreme of turns with a short bed. Many members here like the idea of a slider to be on the safe side in case they do need to execute those extreme turns. As for clearances over the bed rail, you want to aim for 6" of space between your bed rail and the 5th wheel. That's basically the clearance between the floor above the kingpin and the top of your rear bed rail. You'll want to measure this height with the 5th wheel level and try to get a truck which has its bed rails at least 3 or 4" below the floor *BEFORE* they're hooked together. The truck will probably squat a little bit once you hook up the 5th wheel to it.
