@Burb2500
You're going to need to set that kit closer to 6" to fit 35x12.5. My tires are 35s, but 11.5" wide which help with the fit.... And as you saw I still trimmed a lot.
Rear block height is not hard to figure out.... every vehicle is different, so go measure yours. You know your front is going up around 6 inches, find out where that puts your fender heights then measure the rear. For a 2" block to provide a "level" look, your front will need to be sitting 4" lower than the rear stock.
If you're towing, the you know you'll want it like mine, an inch or two taller in the rear so it's level while loaded (and not relying on airbags to do all the work). You might also want to consider getting the 4" deaver leaf springs instead of blocks if you need taller than a 3" block. That's my personal limit on block height for a tow vehicle. No block is ideal, too tall and you'll get axle wrap. Not sure where the "too tall" line is, but gut feeling has me comfortable keepin it at 3"
Lifting will obviously effect towing. you'll definitely want to regear. From there pay attention to stability and handling characteristics
