F150 and Reflection 150 series?

The only issue I can think of for you would be the height of the 4WD bed. For some strange reason all of the big 3 auto makers have raised the height of their trucks and made the bed a few inches deeper!! Who knows the reasoning behind this design. Pulling a 5th wheel will make it sit high in the front and put more load on the back axles. I was pulling my 31' Grand Design Reflection with a 2WD Ram and recently bought a new 2WD F250 to replace it. I was concerned about bed height. As it turned out this new F250 sits a little higher than my 05 Ram but not enough to make a difference. As far as the pin weight and vehicle weight your old F150 should do the job if it has Max Tow I would assume all specs are in range. I was talking to a fellow two summers ago in Colorado who was pulling the same trailer as mine. It's a 27RL Reflection and supposedly half ton towable although I towed it with a 2500 series Ram. He claimed he had no problem with the Rockies!! His was the 3.5 Eco Boost with Max Tow. I can tell you for sure that a 5th wheel tows much better than a bumper pull trailer. Winds in Utah 4 years ago proved that to me!!