37x12.5x17 on stock rims

[Indy]

Stock keys adjust about an extra 0.5" to 1", depending on how they were set up from the factory. You could always get aftermarket keys if you want to go a bit higher. To adjust the keys, unload the front suspension and turn the bolts holding the keys up (about in the center of the car, where the torsion bars end). 37's should clear with minor rubbing on the frame and a-arms, but just very minor rubbing at full steering lock. Shouldn't cause much problems. There are also spacers available for the rear springs if you want to raise the back of the Hummer. If you want to mount the tires, bring them to a truck shop. That's where I had mine installed. They mainly do tires for big semi-trailers and other heavy machinery. They have big balancing machines and should be able to properly balance the tires. Good luck with your tires. Cheers, Indy.