[SCOTI]

Originally Posted by PGSigns

So the 6 lug axles and a 12 bolt tells me its the stock rear. With 4" of back spacing I have less than a 1/2" on the inside with a tire with about the same section width. So you will hit on the inside with that wheel and tire. The tire you are looking at has on average a section width of 9.6 a tread with of 8.5 and a height of 28.7. The tires you list for the front have a section width of about 7.5 and a tread width of 6.5 with you listed height of 26.5. They are a ton smaller and the new tire/wheel combo is going to be tight. What rim are you running in the rear? How much back spacing does it have? There are tools out there that allow you to pick a tire and use the tool to find what wheel you need to run to make it fit. This is about the least expensive one out there. https://via-autoworks.my-online.stor..._19291782.aspx You can shop the tire dealers in your area for a used tire in the size you want to run and use the tool to get your measurements. Will save you a lot of time and maybe a lot of money after buying wheels and finding out they dont fit. This way you will know that they will fit your truck as all tricks are a bit different. When I fit wheels I pull the springs and set the suspension at ride height and see what works checking at lock to lock in the front and with the suspension compressed a couple of inches.
Jimmy
Jimmy

The 6-lug 12bolts came in 2 different lengths so using 6-lug axles as a definitive marker can still lead to disappointment on lowered trucks that are tight on space. If it's 6-lug & 17-spline axles it's pre-65 & most likely the shorter 12bolt or GM corporate drop-out style.

The distance between the backing plate anchor pad to the C/L of the truck arm U-bolt is the best way to know for sure. I only say this having had a buddy that 'assumed' it was an original 12bolt under his truck (because it was 6-lug/12bolt) only to find out after purchasing wheels & mounting/balancing the tires that it was a swapped 12bolt rear from a late 70 model.