Dignan,
After talking with RangerX about this I would not run 12.5's on a 10" rim. An 8" rim yes, but not a 12". You stand a better chance of not popping a bead with a 8" then a 10" rim. There is more protection for the rim with the tire spread out more. I just got 15x8" rims for my 35x12.5R15 BFG KO's and after looking at them mounted, I'm glad I didn't get the 10" rims.
BigT,
Most people with pre95's, that are running 33's are running a 5.5" lift. I am assuming that since you are a student, money is a big factor, thus the body lift and not a suspension lift. I would say if it must be a body lift then get the 3". You might have to do some minor trimming and you might not, it's one of those things where you just have to try it and see. Some people have been able to do it and some have not.
There are 2 sizes of rims for Explorers
XL,XLT are 15x7
Sport,Limited and Eddie Baurer are either 16x7 or 16x7.5