I've been running an under strut level with a zone 4.5" for a few years now without any issue. I had a .75" under there and swapped it to a 1.5" about a year ago to clear 295/65r20 on factory wheels. I don't know what it'd do with the 6" kit though. As far as I know the brackets are the same for both kits, only the spacers are different, so you may not want to push the 6" kit any taller.
Freshstart12 it looks like in your photo your tires are 275/60r20
I was running 275/65r20 on stock wheels that had a +27 offset with a readylift 2.25" level and had slight rubbing on wheel well liner.
But after doing all of the research before going with that setup it seemed I had more rubbing than most, I'd go for it.
Zone 4.5 with a 3/4" spacer under the strut. Rear has zone 4" block with aal.
275/65r20
On a side note would not discourage anyone from installing the lift themselves took about 7hrs for 3 of us not rushing with jacks and stands.
Been wondering the same thing. Discount also inflated mine to 40 psi but the fronts almost look a little low. I have read where a couple guys are running around 55 in the front and 50 in the rear. I'm going to play around with it the coming weeks and see how the ride is affected.