biggest tire that can fit in minitubbed a-body?

Steel wheels from a 2002 volkswagon jetta will fit if your bolt pattern is still 5x4"...all joking aside, here is a good link for determining the backspace of the wheel you want to run http://www.rsracing.com/tech-wheel.html

Decide what size tire you want to run first I think that's in there somewhere. You need to pick a rim width and then take into account the distances of things like your springs, frame and such from the wheel mounting surface. The backspace is going to send the center of your wheel/tire combo in or out.

What you might want to do first is pick a tir wide. An old trick...tie a log nut onto a string, tape one end of the spring to ur quarter panel top center o fthe wheel opening and let the string dangle until it rests. Measure the distance from the string to the closest thing in your wheelwell and thats how wide of a tire you can go.

Check out that link...but start with a desired tire width.