I have a 2003 F-150 4x4 with an RCD 5" lift kit. I am currently running 33" BFG KM2 tires. I know I can go up to a 35" tire, but I really want to go up to
37" tires. What is the best way that I can do this without using a body lift. I have a Rhino-liner, so the body lift is not an option since I can't get to the bed bolts. The RCD had an add-a-leaf, so that isn't really an option. I was thinking maybe torsion keys and a bigger lift block in the rear, but I have heard bad things about the keys. What do you guys suggest?

 

Crank the factory key's for free, if they're not already it'll net you like 1-2" of lift. Then you just have to get an alignment. DO NOT get the aftermarket keys, they're complete junk.

Otherwise your only option is to scrape away some rhino liner to get to the bolts and respray those spots.

 

I thought about cranking the torsion bars, but is that ok for the truck. I thought it made the ride really harsh. What should I do in the rear? Do you think 1-2" in the front will get enough height for 37" tires on a 17x9" rim?

 

It'll keep you in factory spec, but yes it'll make the ride rougher, not unbearably though. As for clearance it all depends on the back spacing of the wheel and tire of choice. It can be done with some, it can't with others. It depends on the tires true measurements not what it says on the sidewall, as well as how aggressive of a tread pattern you decide on.

As for the rear since you already have an add a leaf, your only other economical options would be a bigger block or lift shackles.

 

If you start hitting the underside of the bed bolts every couple days with wd 40, and do it for a month or so, you can probably simply undo the bed bolts. I have had great success with just digging out enough liner out of the torx socket contact area of the bolts, and slicing an "x" pattern on the head of the bolt. If all goes well, and you can get the bolt turned out without busting the "nut" through the retainer, it will go back in place perfectly, and sit on top of the liner.

 

Your best bet is a body lift.
As for the aftermarket keys, they do the same thing as cranking up the OEM keys only worse. They allow you to put even more preload on the torsion bars than you can with the OEM keys.