I started wondering about this last night when my buddy stopped by with his 85 Runner. I was looking over his truck and noticed some rub marks on the rear frame rail, asked 'hey, do the tires rub in the rear?' 'yea, I don't worry about it.'
So his rim and tire combo is 33x12.50R15 MTRs on some 15x8 steelies with 3.75" of back spacing. I start to worry a bit.

I plan to run 37x14.00-15LT Iroks on 15x10s with 3.75" of back spacing on my my 82 Pick up, am I going to have rubbing issues?

 

I would say it depends on how much lift you will be running.

 

Uh...no.
I'll be at about 4" of lift, I can cut sheet metal. The frame on the other hand.

 

Well, if he does, I'd say you will...

 

Yep, tires will rub the frame in back with the stock axle and 3.75" backspaced wheels if you have any flex at all. Wheel spacers, or a wider axle or wheels with less backspacing will fix that.

 

and the money just keeps getting added.

 

i ran 35x12.50s on my 79 for a week or so, STOCK SUSPENTION..on 15x10 alcoa wheels..unknown b/s, and they did rub a bit on the frame, though my 33x12.50s didnt rub, i would asume a 37x14 tire would rub, best bet is the IFS axle

 

I run 33 12.5s on 10 inch rims with about 3 or 4 inches backspacing the rub the frame a little with my 3.5 lift and no bump stops. My friend runs 36 15 swampers on 12 inch rims with the bump stops lenghtened and he doesn't rub. Extending the bump stops is your best bet if you are worried about rubbing. You loose uptravel, but a good suspension makes up for it in droop. I dont mind sacrificing my rubber for the extra flex, its personal prefrence.