I'm running a 0 offset (4.5 backspacing) and I am very positive the offset of the stock rim would never work on a 12.5" tire. I have maybe an 1.5" between the UCA and tire.
Ill get a picture soon.

 

I am figuring that w/out spacers, they will likely rub the UCA, as you said. However, I'm curious if they only rub on full lock, and that I can avoid any real "issues" as long as I don't go full lock.

My real issue is, if I have to use the spacers, I'll likely end up "needing" some extended fender flares. I love the way those look when you have a wider stance, but don't really feel like spending the $400 for the flares, then another $200 or so to have them PTM.

It's funny how one mod leads to another, then another, then another ... it's like a never ending story LOL.

 

Here you go .