72-75 Jeep Alloys Factory backspace

I am looking for the factory backspace specs for the jeep 15x8 alloys (slotted mags)

before everybody jumps down my throat..
there are 4 different part numbers for slotted mags.. 2 15x7 and 2 15x8 numbers..
im looking for the 15x8

I am ordering some 15x8 TR alloy wheels for my CJ6 project..
they offer 3" and 3.5" as optional BS.. I would like to know what stock was before I get to crazy..

I plan on running 33x10.5 tires... had a brief thought today of metric 285's and 17" wheels.. but I think that would look awful goofy on the Jeep.

 

Are you worried about function or authenticity? Either backspacing will work.

 

function...

I understand either will work.. I guess im just looking for a benchmark..
if I knew the factory was X then I would have a good idea how much farther I would be going with the option I go with..

 

also is there an issue clearing 82 CJ disk brakes?

any info would be great

 

Potentially. Not sure which backspacing I have but the factory slots I have interfered with the 2 bolt brake calipers. 1" wheel spacer did the trick