Wheel, tire,offset?

Ok, so with 15's and 73+ BBP disks up front and BBP axles in an 8 3/4 out back, with a stock or slightly lower ride height you'd be looking at-

15x7" up front, with a 4.25"-4.5" backspace. 225/60/15 is about the best you'll do, if you go taller than ~25.6" on the tire height you'll get into the lower front corner of the fender unless it's already been modified. 215/60/15 would be easier, especially if you want to lower substantially.

In the back, 15x8" with 4.5" to 4.75" of backspace, and you can run up to a 275/60/15 with the stock spring locations. That will be pretty tight, so if you're completely unwilling to do any quarter lip rolling you may want to stick with 255/60/15's, just to have a little breathing room because of the fairly lax factory tolerances on these cars. Lots of folks run 275's though.