Help! Backspacing on Factory 15" 4 Nub 6 Lug Steelies

[ShortCST]

So I've now purchased three individual 4 nub 15" factory steel 6 lug wheels to replace my front drums on my '68 C10.

And I don't yet have a matching pair.

The 3 nub wheels on my truck came from the factory with 4" backspacing (could be 3 15/16?).
The 4 nub "disc" wheels sitting on the floor of my house appear to all have different backspacing.
One has 3.5" backspacing, one appears to have 3 13/16" backspacing, and one appears to have 3 15/16" backspacing. I'm looking at one on eBay that the seller claims to have measured 3 7/8" backspacing.

I've spent over three hundred bucks so far, and don't have a pair to send to the powder coater.
How many different backspacing measurements did these wheels come with? Should I just buy the wheel with the 3 7/8" backspacing off eBay, and match it up with whichever wheel I have now that is closest to it (3 13/16 or 3 15/16)? Is one or two sixteenths of an inch difference not important?

Thanks guys

[ShortCST]

Anybody? I've had the truck on jack stands for weeks, trying to get this sorted.

[geezer#99]

You're splittin' hairs!!
There's always differences on the rolled edge.
Measure from the bead on the rim where the tire mounts.

Also have you checked the front spacing or measured the rim width. There's nothing absolutely precise on a steel rim. They aren't built like billet wheels.

[ShortCST]

Ok, thank you geezer. That's what I needed to hear. That makes sense. I guess I was just wondering how many different backspacing measurements those wheels had. I'll check the front spacing when I get home, as well.

[geezer#99]

Another thing to check is if they're straight.
Mount them up on a hub tourqed into place, build a jig of some sort to check on different spots for how straight they are.
It won't be absolutely accurate but it might save wasting money on a badly bent one.

[sambrutay]

I have had the in 3 9/16 back space and 3 13/16 back space.

[ShortCST]

Thanks Bruce. You wouldn't happen to have another of those 3 13/16" backspaced wheels lying around perchance, would you? The EBay vendor reports a 3 7/8 backspace, but I don't know if he's mismeasuring, or if I should just just buy it and try not to obsess over a sixteenth of an inch. It's hard for me not to obsess when I'm working on something; I'm just that kind of guy.