I tend to try and keep things simple, yet effective. Follow Tim's wheel tire advice...
I wouldn't plan on towing with 37s without upgrading to at least slotted rotors and a gear change. You will also want to crank up torsion bars and add the Cognito Pitman and idler arm kit to keep from rubbing and wandering on the road.
The slotted (not drilled) will help keep brakes cool and prevent hazing under load. You could add performance brake pads later if you feel you need them.
Hopefully you aleady have a weight distributing hitch and trailer brakes for your RV, so all you will need is a longer shank with adjustable drop. Try looking at these shanks by Reese:
http://www.towpowerbyreese.com/
Do not jump on board the performance enhancement bandwagon if you do much towing. Most will cost you low end torque performance. What I would suggest (I hardly ever do this) is to leave everything stock and add a helix power tower throttle body spacer to bump up the low end torque.
Exhaust and air intake upgrades will cost you low end torque.
Only other thing I would suggest is a hand held programmer which will give you the speedo adjustability for tire size changes and top end performance to climb hills without sacrificing low end. It will also give you some shift point control.