Instead of doing something haggered with hockey pucks on such a new truck(more on that later), why not do it the right way?
Summit Racing offers a 98+ bodylift kit for a whopping $143.
http://www.summitracing.com/parts/SUM-7888300/
Take into account Summit's supplier, Performance Accessories offers their kit at a $270 price...
http://www.summitracing.com/parts/PRA-70033/
That should make your decision alot easier. Both kits come with everything needed except manual shift extension. Only real difference between the '98+ trucks is the fuel filler neck and the fuel vent tube sizes. Which could easily be cured with a trip to Home Depot plumbing department or your local hardware store. And best part about it, it's been done countless times on trucks not listed to fit that Summit Kit....but it does. No bologna about trying to find the correct bolt lengths, making bumper relocation brackets, the steering shaft extension(safety first...steerings kind of important, lol), not to mention the excellent instructions the PA kit comes with(which you can download for free and use during Summit kit install).
I've been in your shoes before... IDK how old you are but with a 2011 truck, and with only 3hrs of work a night, I'm kind of assuming you may be young and in school? I would be VERY thankful for having such a nice new vehicle to drive. I was 17 about to turn 18 when my parents co-signed the $10k loan for the then 3 year old truck that graces my avatar. I was making less than you are and managed to make little mods here and there while still making the payment and insurance. In your shoes without really knowing any details about your case(lol), I suggest a torsion twist and 32's and call her good. I didn't start really dumping money into mine until I had already owned it 4 years and had just paid her off. If my assumptions are somewhat factual, just save it, DONT HACK/HALFASS a new truck, and the point is.....
If you're gonna do it, why not do it right? $143 ain't much. If you can't afford that, you certainly can't afford the astronomical price of larger tires for your 18"(?) GT500's.
Again, I am assuming some things and hopefully someone doesn't read this and dig way too deep into my logic here, just trying to give some helpful advice. Hopefully when you read my post, you'd understand what I'm trying to say.