Which Hitch?

x2 on the Andersen Ultimate (I've had mine for 14,000 towing miles so far and its great). Now for my thoughts on truck shopping.

Know the actual pin weight of your trailer. If possible take it to a CAT scales (might be hard if you don't have a truck yet). Any truck you buy will need to have sufficient payload to accommodate both your hitch and your trailers pin weight (and probably about 500lbs for passengers, fuel and luggage).

Pay attention to the trucks sticker that lists 'Payload' (but also note if there have been aftermarket additions that would reduce that payload number (ie gooseball hitch, nerf bar steps, folding hard tonneau cover, airbags). If it's a 3/4 ton (ie 2500, 250 etc) and you can CAT weight the truck alone, Payload is equal to 10,000 minus the trucks CAT weight.

One of the reasons I ended up choosing the Andersen over other good hitches was at 32lbs it didn't eat up as much of my available payload. The other reason was because it easy to remove from the truck bed by myself when I'm not towing.

You may find these two graphics of my stickers helpful:
Trailer Weight Sticker Composite
Truck Stickers and Andersen Turn

Look at the Anderson Ultimate Aluminum hitch that attaches to,the ball in the box of the truck. It ways 35lbs and rated for 24,000 lbs. I have one it's great.

If some of those trucks have bed rails with the gooseneck ball plate on the rails, several 5th wheel hitches will fit the same rails.

You would be better off going with a standard 5'er hitch. Those adapters put different loads on the 5'er frame than it was designed for.

I would not use that type adapter, for reasons mentioned above. There are several FW hitches that will attach to a ball system.

You don't say how new of truck you are looking for, but the later models with the puck system for attaching the hitch, are a great option.

Jerry

Safe ??
Depends on the trailer mfg recommendation as not all 5th wheel rv trailers frame at the pin box attach area have can handle the leverage forces from a GN adapter....some trailers can and probably most can't.

Only your trailer mfg can answer your question.