Right now I am running a 35" tire that is 12.5" wide and have a little rubbing lock to lock and was wondering how much more rubbing there would be if I tried a 36" or 37" tire that was 12.5" wide.

If not, what would be a good way to get another 2" on top of the 3" spindles and 3" body lift so I could fit the bigger tire?

 

You will rub a lot more with a taller tire. You can install Daystar coil spring spacers to gain an inch or two of lift.

 

See, the 2 4wd shops over here told me there was nothing left to do. How hard is it to do this myself? Or if not myself, then to buy the spacers and pay to have them put on?

 

You have to remove the coil springs and reinstall them with the spacers. You may also need an adjustable camber kit to get your alignment correct.