When you buy a used 5th wheel private party...

Most of the later model FWs have a front cap designed for 6.5 bed towing. Yes the Ram has the shortest distance from rear axle center, to back of cab. If you install your hitch, set in rear most position, just to get it home, it should work without issue. Yes, as mentioned, caution when turning/backing SHORT, will be necessary. When you get the Sidewinder installed, it will be a non-issue, and you can put your hitch in whatever position works best.

Jerry