wondering how well 28" tires will fit in a stock suspended 10 bolt 4th gen? Ive got a set of 15 x 8's but the backspacing i believe is only 4.75. Will they fit the wheel opening or would I need the full 5.5 backspacing?

 

Depends on the 28's. I ran Hoosier QTP 28x11.5-15's with the only problem being having to move the axle back about 1/4" when the front surface of the tread started hitting the metal at the front of the wheel well, when trap speeds went over 125mph. Yet a set of 28x10.5-15W ET Drags required removing about 1" off the leading edge of the rubber bumper cover. The ET Drags seemed to grow more. That was with a "stock suspended" 12-bolt, but I don't think the difference between a 10-bolt and a 12-bolt will affect whether the tires fit in the wheel wells.

The 8" wide wheel with 4.75" BS will move the outside edge of the tire out about 3/4" farther than this:

 

I run twentyeght'' drag radals stoc suspended 12 bolt wth no fender mods at all because they don't grow.

 

I ran some on a 15x8 with a 5.5 backspace. I will be one to say not all slicks are the same. My M/T grew alot and I had to move the rearend back and they still rubbed the front and the bumper needed trimmed. I've seen other people run hoosiers and they did not rub.
I had them on the ten bolt until I killed it with 1.48 60' times leaving on 200hp with a cam only longblock. You will most likely need adjustable LCA's if you currently don't have them.

 

Im running 28s and for me the adjustable lca's was a must have to get them to fit. My axle was to far forward to fit on stock susp.