rear wheel backspacing when sitting pinchweld on the ground

[G-NUT]

What is your wheel backspacing when using Porterbuilt suspension components? Narrowed rear axle?

Online & in magazines I see squarebody trucks with wheel backspacing that I like and don't like. I am installing a complete Porterbuilt extreme (level 3) suspension on my '85 GMC. I like the look of the Reyna Brothers Orange/White truck's wheel setup.

What I'm planning on running are 24x8.5 front / 24x12 rear Raceline wheels. There is the possibility that I'll run a 24x9 front / 24x12 rear U.S. Mags wheels. And also, depending on some things I may reluctantly run a 24x10 in the rear.

I'm curious to know what would be the best offsets for this and how much people have narrowed their rear axle for this.