68 Fleetside Wheel Backspacing

[Dub Silverado]

I am about to order a set of 3 piece wheels but want to make sure I get the size right. I want to run a 8.5 wheel up front, and a 10 inch wheel in the back. Can anyone give me the proper backspacing for this combo on a 68 Fleetside? I have searched but found too much random info that contradicted

Oh, here is a picture of the project as it sits now, and the Chevelle is our project from last year.

[Sinister]

Can't help on the backspace, but those are some sweet rides.

[69chevybmx]

i currently have 15x8 et-19 (3 6/8" bs) up front and they are pushed about to the outer limit. You could probably get away with 4-4.5" bs up front but then you run caliper clearance issues depending on the brake kit you have.

For the rear you might be able to get away w/ 15x10 et-46 (3 5/8" bs) and not rub the fenders depending on tire size.

[Mondo]

On my 67, this is the backspace I have for 15 inch rims and front discs (I think bigger rims will give more clearance over calipers): 4.25in in front and 4in in back... 8 & 10 inch wide rims. I think early trucks (like mine) had a more narrow rear end needing an inch less BS (and adding to the confusion when reading all these threads).
I have 275s in the rear... the rims can handle bigger but I think a larger tire would rub so you might want to factor that in (a higher truck might clear the fender too). It's always better to have a little too much backspacing as you can add spacers... go the other way and your screwed.