Having trouble finding a spare tire

[BanjoBob48]

I've been looking for weeks for a 15" rim to use as a spare for my 1970 C10.
I called every junk yard within a reasonable distance, and no luck.
I just got my truck, so I'm kinda dumb about what might work.
Like I said, it's a '70 C10 w/ 6 lugs.
I have deep dish chrome rims on her, and I'm running 265/75r15's in the back,
I'd guess the rims are pretty wide. I put 235/75r15's on the front so they wouldn't rub, and I assume I need to get a spare that is pretty close to the 30.7" height of those rear tires, so it doesn't cause problems by being too drastically smaller. I've heard if the spare is shorter that it could cause problems with the rear end.
This means (I think) that I need a rim that's wider than the stock 5.5 or 6 inch to fit a tire that will give me the greater height.
I've been looking on eBay and see rims made for the Colorado/Canyon which have 6 lugs and 5.5" spacing.
Would these fit?
I was told the center hole can be a problem too, but mine's a 2 wheel drive, so does it matter???
I mighta been a bit hasty putting on those 75 aspect ratio tires, now I have a ride that's squirrelly on the highway on windy days, and my accelleration has suffered as well. On the other hand, I'm not as tempted to act up, and those new Goodyear Wrangler SilentArmor's do look nice.
David