[CC69Rat]

Tell us more about your truck. Is it dropped? If so, how much? Will it have more of a sporty feel or stock? Do you like a taller sidewall, or minimal sidewall?

What year is the truck? Leaf springs or Coils? ..

Tire size calculation:

Example - 255/50/18

255/25.4 - This gives you the width of the tire in inches. - 10.04"
255/25.4*.50 (aspect ratio) - 5.01" sidewall (from the ground to the bottom edge of the wheel)

So, 255/25.4*.50*2+rim size. 5.01*2 = 10.02"+18 This tire would be 28.02" tall overall.

Not assuming you dont know .. just trying to help. this way you can nail it the first time. That's why I was curious how far it was dropped (if any) and how you planned to drive it (sidewall flex)

Also, do you know which rear end housing you have in your truck? It can change your backspacing around a little .. you want to make sure if you have gotten these backspacing numbers from somewhere else (?) that the two trucks have the same rear axle housing. On the numbers you posted up, I am assuming you have the late rear end. Late 70-72.

I can elaborate if you need the info.