What backspacing for 15"x8" steel wheel?

[Fett]

I am in need of an 8" wheel for my slicks. I currently run 26", but may be sizing up to 28". I currently have my slicks on Ford steel wheels that are 6.5" wide, but need more grip.

Both Summit and Jegs have steel wheels for like $40 a pop, but I don't know what backspacing to go with. I have stock length rear axles (drum), and it is slightly lowered with flipped quad shocks, and no tail pipes. I run 275/40/17 drag radials on the street, and I have plenty of room between the tire and fender, but it is a close fit on the back side of the wheel.

Short version:

What back and offset should I go with to fit a 15"x8" steel wheel in the back that would accommodate a 26" slick and would work with a 28" in the future?

 

[MeanGreen]

4.5" the wheels will stick out slightly thru your fender wells. 5.5" and it will be nicely tucked. What ever look your going for there ya go

 

[Fett]

What about offset?

I need to look at how my slicks sit in the well now to decide which backspacing I need....but how does offset effect it?