Origonal K Series Rim Offset ?

[Billhilly]

I have found a set of rims down here that are meant to be off a 72 K20. Haven't been able to get a picture off the guy yet but he says they have 5 1/4" back space.
My 16.5" rims that aren't origonal are 4 3/8" and another (nearly) inch would put the rim edge and wheel weights almost on the tie rod ends.
The wagon wheel rims I was going to use are only 3 3/8" backspace.
So was there a semi standard rim that went on 72 K20's, or K2500's?
Maybe his rims aren't origonal either. Any thoughts on the matter appreciated, before I fork over $$!

Bill.

(VERY hard to find parts down here, so I can't just go to the bone yard).