76 2500M backspacing?

[Dragnet]

Curious if anyone knows the backspacing of the stock T-slot wheels and if a wheel with a larger backspacing will fit on a 2500M? I am looking at 16x7 front and 16x8 rear rims with 3.5 inch backspacing. Any idea if they will fit? My measurments show about a 3.25 stock backspacing on the T-slots, but just wanted to confirm this? I will probably run 205/45-16 front tire and 225/45-16 rear.

I know each individual car is a little different, but I don't have the opportunity to fit the wheel before buying as they are on-line and not local.

TIA.