front discs backspacing

[Bobby326]

I have a 67 lemans with front disc brakes from the rite stuff. I believe their the stock D52's. Does anyone have these brakes and can tell me what backspacing you need to run an 8/8.5 wheel. Im putting on an 18x8 or a 18x8.5rim with 245/40/18 tire. I have read that i would need a 5' backspacing. Can anyone who has 18" wheels verify this for me thank you for your help