The worse your tires, the more help you need to get traction...the point of extra articulation is to try to keep your tires on the ground...the more droop you have, the easier that is...and, longer shackles can do that for you.
If you install shackles...you need to raise the front end the same amount to match..or you will be driving around with your butt in the air...
To raise the front end to match, you adjust the tension on the torsion bars...they have an adjustment lever built in, as t-bars tend to sag with time, and its normal to tighten the tension from time to time. (This is free)
Once your truck's ride height has been raised 1.5" in front and in back, the steering and the angles that the tires contact the road have been changed...so, you need a new wheel alignment ($30-50) to get things back where you want them (The truck is designed to adjust these changes as well, and an alignment is a good idea from time to time to restore steering geometry, tire wear, etc.)
So - A PML is t-bar adjustment in front, and new longer shackles in back, and a wheel alignment.
Also - Advice: Sell The Grabbers before you destroy them, and use the money to defray the cost of new tires, rather than purposely destroying them, not enjoying the process, and paying for new rubber from scratch.
I sold my Grabbers to the tire shop at 7K miles, and got over $50 each for them. I sold the spare on the steel rim to a fellow wheeler for $75....
That's $275 towards new rubber, rent, or whatever you need.
Actually - Here's my plan for you:
1. Find a tire shop who will take the tires in trade for the rubber you really want...and does wheel alignments.
2. Get the new shackles, and do a t-bar PML, and go to the shop for your re-alignment and new tires...use trade in $ to defray cost of alignment and rubber.
3. Drive home from tire shop with PML and new rubber on.
I bought a set of four matching alloy rims for $200, so I have a total of 8 aloy rims, 5 with 33's on them...the Grabbers essentialy bought the new rims, so now I have the option of mounting a daily driver tire set and an off road set of tires, and or replace stuff if I break it, etc.
For you, maybe just rading in the spare rubber or one the same as the other four, but keeping the spare rim would be better.
If you only get 4 new tires, (Not 5) and have the Grabber as your spare, and you are out somewhere that that the rubber failed and you NEED a spare, think about if the Grabber will get you OUT again....if the terrain killed the tires you REPLACED the Grabber with...
Lots of people take the chance, and its a roll of the dice as to if they wish they hadn't....mostly, if you can't afford five new tires, but you can afford 4, that's when you get 4.