33's are fine on the front D30, they're even ok on a D35, it's bigger than 33's that you start running into problems. There's a metal tag on the rear diff on the left side, you can see it in the pic. It's held on with the 8:00 and 10:00 bolts. Clean it off and look at the #'s embossed in it. They will be hard to read, but with enough light you can do it. The last 3#'s are the gears, they'll read 3 73 or 4 11 most likely.