Well I might be able to help.... I currently have two complete sets on wheels and tires for our vx. I will try to give you details.... more of opinions than tech data.

1st set... 16x7.5 (oem zu) & Dunlop Mud 265/75 R16 (probably 6 ply std)
2nd set.... 18x7 (oem zu) & Dunlop Max Traction Mud 275/65 R18 ( 9 or 10 ply)

future set 275/70 R18 Goodyear Wrangler MT/R (9 or 10 ply)

The 10 ply tires are designed for big Chevy like duellies, much heavier vehicles.
I have put almost 50K on the set of 5 (2nd set), I had them balanced two weeks ago. Average tread depth was 15/32, barely any wear. I run about 40 psi on the street, drop down to 22 in the mountains.