What backspacing for Weld Draglites?

It's good to be back to the site. I have been at ford-diesel.com looking at stuff for my Powerstroke Diesel. If anyone out there has a Powerstroke Diesel, check that site out.

Anyways my buddy was going to buy Draglites for his car, and I was wondering what backspacing he should buy (he has an '89 notch). I have Draglites, but I bought them used and am too lazy to take them off to measure the backspacing.

Good to be back to this site.

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88GT stock shortblock, ported GT-40 iron heads, Edlebrock Performer intake, 24# inj, Pro-M 75mm Bullet MAM, 3.73, hurst short throw, F-303, electric fan, alum rad, FMS HD clutch, R134a ac conversion, 70mm TB , and some other stuff I probably forgot, best run so far on ET streets is 13.02@106 with a 1.87 60ft Only been to the track once still alot more tuning to do and need more driving experience.(Full body weight GT, full tank of gas, and sway bars connected, gonna disconnect sway bars and dip