Unfortunately there were at least 6 different transmissions used in these trucks and 5 potential gear ratios were available so "stock" doesn't tell me anything you'll need to find out what you have and post it up, but that's easy enough to do just find the trans and axle codes on the drivers door calibration decal.
The reason that's important is because some of the transmission don't have an OD ratio and those that do vary a lot and that will impact the gear ratio you're going to need for 37" tires.. which is gonna range anywhere from 4.10 to 5.13.