the joys of older campers in newer trucks 😅
I have a 1991 slumber queen in a 2014 F350 and I had to build a double layer frame out of 2x6 boards to lift it high enough, so that is a 3.5" lift. start with that, get about four 8 foot 2x6 boards, jack up the caper a bit and place them along each side then lower it on to them. see if you get some clearance on your rails and your roof. if so that is a good hight, if you need another little bit you can add a horse stall mat under it and even on top if you like. they are normaly 1/2" thick so that would give you another 1" if you use two. I am going to redo mine and put 3/4" plywood on the bottom of 1 layer of 2x6, fill the gaps with foam, then another layer of plywood on top. that way I will get some insulation value to add to the floor. or i might just sell it and buy a new one, fingers crossed.