Looking for correct Backspace for 15" rims

[Quik393]

Ive searched all over this site and I can't find any information on what backspacing to run on a 15x8 rim for the rear and a 15x7 front. I'm planning on getting Weld Pro Stars or Draglites. My main concern is I don't want the rim sticking out of the wheel well, I like a tucked in look.

Mike

 

[twin 93 svt]

3.5"

 

[QWKSLVR_2]

Yup, 3.5" fits perfect. Don't listen to the Weld wheels Tech either, they don't know what they are talking about.