What you need to know about CCKW tires and why it is important.
Read it, understand it, and practice it for your Jimmy's sake.
Probably thee most important thing you need to understand about
a CCKW, regardless of cab type, body style, or drive-train type is that
the rear tandems are in 8 wheel drive ALL THE TIME.

Let me state this a different way: The rear tandems are in 8 wheel drive ALL THE TIME.

Yes, I said the same thing again. Now remember this. it is VERY important.

If you do not choose your rear tires and tire rotation policy correctly, you
will cause wear, sometimes great amounts of wear to the CCKW drivetrain.

First: Make sure that the rear tires, at least the ones that the truck rides on
(you can run smaller diameter tires on the inside) are all matched as far as
diameter, or better yet circumference is concerned. If you run different sized
tires in any of the 4 wheel positions, you will have the two axles fighting between
themselves through the two (actually 3) rear drive-shafts, 6 universal joints,
3 slip joints, the pillow block bearing, and the transfer case!

Best case: If you can, buy a new set (8) for the back and leave them alone till worn out.

Next Best Case: Buy 4 new tires for the outside positions and run smaller, older tires
on the inside positions.

Lesser Next Best Case: run matched tires on the front and rear of one side
in the rear and another matched set on the front and rear of the tandems on the other side as long as the difference is not too great

Worst Case: Run all different sizes....

Second: Do not EVER rotate the rear tires to different positions! The front tires will
last between 3 to 5 thousand miles depending upon how you take corners. The
rears will last around 20-30 thousand miles. Keep replacing the front tires. Do
NOT swap them with the rears, EVER.