will the open country mt 35x12.50r17 fit on a stock 08 dodge ram 1500 17" rim?

 

Has been done, but not recommended. You should have an absolute minimum of 8.5" wide wheel for a 12.5" wide tire. 9" would be better...

 

Well I have an 07 mega cab 1500 with 33x12.5 on the stock 17s. I have not had any problems but have only had them on for about 3-4 months. I went with the pro-comp all terrain

 

I'm surprised you got a place to mount them, I know most shops in my area either won't or will make you sign a waver that you know your wheel/tire combo is out of spec. Although you aren't far off, I believe the stock 8 lug 17" wheel on the Megas and 2500s are 17x8 with 8.5" being the recommended minimum to run a 12.5" wide tire.

You'd probably be fine although I'd be wary of the tire coming off the bead if I aired down to much to go off-the pavement...

 

Aside from the rim width being slightly out of spec, I think the tire will rub on the upper ball joint areas of the A-arms. At least they did on a newer half ton I sold a set of 35x12.5x17's to. His choices were either wheels spacers or new wheels. There was just too much backspacing on his stock wheels.

Check out the clearance from your current tire to the upper A-arm area.

 

i have the wheel spacers due to the 6" lift i needed to push the stock rims out so there was no rubbing but i only have 285/70/17 right now

 

I had 35 12.5 17's on my stock 17's on my 03 Ram 1500. They fit fine, and the shop never mentioned anything about them being out of spec. It was only temporary until I got my new wheels (which were 9" wide) but they looked fine, and I didn't have any problems for what it's worth.