Have you ever attended a pull? I would definitely go to some and take notes if you haven't. If you have, and your looking to keep your truck streetable, you are limited in the mods you can make, but there are definitely 2 that I would make sure you have before you consider driving out on the track. Without these two, you are wasting your time, money, and you will probably get laughed at.
1) a locking rear axle (detroit locker, tru-trac, ARB or similar)
2) tires with meat on them. (not street tires. not mud and snow.)
Without having all 4 wheels turning (at least 3... you probably will not put a locker in your front axle because you want to keep it on the street) and being able to throw dirt, it won't matter what gear you use. You won't move. Also, keep in mind, that's at least 10,000 pounds worth of sled your hooking to. Make sure your hitch is up to the task. More than one guy has been laughed off the track because his hitch ripped out from under him. Also, don't use a drop-step hitch upside down to get more leverage. You will exceed any reasonable tongue weight. Jack the rear up instead... with higher arch, springs. If you can't do that, come up with a crafty way to fix your rear axle so that the suspension is disabled.