backspacing question?

[sneaky]

hey guys,
was wondering if anyone knows which of these i can run on a 72 c-10 long bed 2wd with front disc brakes and rear drums?

for the front i have a 19x8.5 with backspacing of 4.34 or 4.04?
-10.4 and -18 offsets respectively

for the rear i have a 19x9.5 with backspaing of 5.03, 4.73, or 4.54?
-5.4, -13.01, and -18.099 offsets respectively


i am trying to figure out a thickness in the spacers i will be buying. i will have a standard 3-5 coil spring drop, so i shouldnt be scrubbing the fenders, i want more of a flush look, definitely no poke....either right at fenders or just inside them.

thanks in advance, scott.