Any gas or diesel SRW HD truck would be a great match for that small of a fifth wheel. Pick your poison and go camping.
If you're trying to contain cost you could skip the high trim and most of the extra goodies on your list. My preference is to put money towards performance items and skip most of the fluff. I would spring for diesel, 4wd, spray in liner and enough options to get some basic comfort features like AC, bluetuth hands-free, keyless, etc. Drop from the Lariat down to an XL or XLT (or equivalent if GM/Ram).