Unless your truck is built to handle the additional weight/size of the 37 I'd suggest the 35 or metric equivalent. Heavier (and larger diameter) tires naturally have more inertia than smaller tires and this means increased wear, reduced power, and the requirement of stronger (heavier) parts to keep it all together. It takes either a lot of beans or a low (numerically high) gear to turn a 37" tire. I still think the 37's are a big boy tire and if you are running a big boy truck it's okie dokie. I think 35's are more realistic for streetable trucks owned and driven by the not so big boy - anyone disagree?
Now to the differences. Other than the obvious, the 37's use a four ply nylon carcass whereas the other sizes use a 3 ply carcass. There might also be a difference in the center tread patch that runs the full circumference of the tire - not sure on that though.
One last thing... BFG builds lots of "special tires" for the big teams. These special tires aren't supposed to ever make it to the public but sometimes they do. Watch out for some of the special tires because in certain cases they can be many POUNDS heavier than the same size off-the-shelf tire. I remember carrying six of the metric Projects with the huzza guzza Kevlar reinforcement and they were MUCH heavier than the normal tires. That kind of weight difference can cause big problems if you aren't prepared.
Jeff made a very good point. There is no reason to run 37 unless your truck is set up for it. They are great tires, but they weigh a lot, and are terrible to drive down the road especially when they are cold. Your best best bet, if it is going to be building something you are going to drive down a lot, you might want to go with a set of All Terrains or give up some of the nice drive-ability on the road and go with 35 Baja T/A's.
Project 1500, it doesnt matter whether your motor can handle it, anybody can gear something down and run 37 on it no problem, the question is whether you suspension can handle it. If you wanted, you could gear a pinto to run 37's. Gearing and motor are only a small part of the equation. To run a 37 right, you need to have a good set of spindles, steering components, and strong strong suspension components.
don't ever underestimate the effect of bigger tires on braking ability, this is so often overlooked.
going from a 35" DOT tire to the CORR 35" project tire and 17" wheels adds about 200lbs to the truck. that is huge!! i'm sure the desert tires are built just as heavy or heavier than our SC tires. brakes are the single biggest problem with guys running pro-2 and sportman 2, just can't stop the truck with those big tires
"Project 1500, it doesnt matter whether your motor can handle it, anybody can gear something down and run 37 on it no problem, the question is whether you suspension can handle it. If you wanted, you could gear a pinto to run 37's. Gearing and motor are only a small part of the equation. To run a 37 right, you need to have a good set of spindles, steering components, and strong strong suspension components."
I got the suspension to handle the 37's, I got the gears for that tire size,and I have plenty of power.
So I am going to run 37's on a app thunder II 17x8 wheels. If you dont like it its ok you cant see it from your house.
The tires are going on a 2002 silverado 2wd 4.8L 10" whiplash kit with custom powder coating cherry red and 5" and 3" stacked block in the rear, 373 gear ratio, Fiberglass fenders, with a K&N filter (it gave me 15 horsepower for real). It wont have a problem handling the tires at all! It was setup so well and it has coilovers!!!