Reeves1 what rear do you have, mine is a narrowed Explorer rear. it is about 3/4 of an inch shorter than a stock rear.
Was trying to be funny....
Mine is a narrowed 9" with Mark Williams High Torque axles.
Spring center pin to pin is about 26 3/4"
Big tubs.
All of the 18.50 tire will fit under the fender.....but the front & back of the wheel well needs to be cut out for the 29" tall tire.
I have 26" tall right now & it's a tight fit.
I'd stay with 26s - but cannot find any that are 18.50 wide.
Funny....was at the speed shop in the city & the wife was looking around while I was buying a truck load of parts.
Showed her a set of 29x18.50x15 MT tires. She thinks me a little bit crazy