33's will fit with no lift. I ran 33 14.50 Mickey Ts with no lift on my Jimmy and 8" rims. They did rub at full lock on the leaf springs, but 12.5 should not. I still think that the 2 1/2" lift is max I would do with 33's.
4" Rancho front springs, 4" National rear leafs with 35 14.5 Mickey T Baja Belteds circa 1990:
Same lift, but 35 12.50 BFG MTs. The BFG were nearly an inch taller than the Mickeys, this photo in 2000:
