Help with backspacing on wheels

Hello, I'm about to buy some new wheels and tires for my 1997 Tacoma 4WD, and I was wondering what backspacing I should get, the tires I am going to be getting are 31x10.5x15 and the wheels I would like to buy are 15x8 pro comp steel wheels but I don't know what to get for the back spacing. Also, I've read online that only the 87 series fits on the first gens is this true?

 

With a 31" tire BS can be anything you want. I'd shoot for around 4.5". That'll bump them out a bit over stock. Not sure on the series but if the lug pattern is right I don't see what other issue there could be.

 

Apparently the problem is that a lot of 15" wheels especially the soft 8 style will rub on the caliper.