just wondering i have a 91 4x4 short box regular cab whats the biggest tire i can put on this thing without a lift kit. im looking at a set of 31x10.5x15 but if 33's will fit i got a line on a set of those also .

 

33's will fit on a 4x4 without a problem. 31's are the biggest you should go on a stock 4x2.

 

I have an 88 4x4 F150 and 31's rub the radius arm when i turn. It will depend on your rims, I have stock 8.5" rims, Im not sure what the inset is, but that will play a factor. at least it does on mine. I think some places will try different sizes and if they wont fit, then they just go smaller. The pepboys here told me they would do that for me.