Actually, it's the Backspace that is the important measurement. You'll want no more than 3 1/2" of backspace. Offset and Backspace tend to get used interchageably for the same measurement, but that isn't the case. Backspace is the dimension from the edge of the wheel lip to the bakcside of the wheel mounting surface (where it bolts to the hub). Offset is the amount of difference from the mounting surface to the centerline of the wheel. Different width wheels will cause the offset reading to be diferent if the backspace is maintained and vice-versa.
I do know that Dodge truck wheels (pre '93) work alright, and pre-'87 GM wheels should be fine, too. I've also heard that Ford van wheels work with a 3/16" spacer (one of the few times I'll endorse use of spacers).
