Wheels! 5 vs 6 lug, and center hub hole size

[PumiceMan]

Alright guys, I've got lots of questions!

I've got a '69 GMC 1/2 ton, stock and manual everything, 6 lug drums, leaf springs in back. I recently bought and installed the drop spindle front disc brake conversion from CPP, with the 6 lug rotors. I did this knowing I'd probably have to buy new wheels, and it turns out that yes, the stock 15" wheels hit the calipers.

Like I mentioned, I was pretty much expecting this. On a whim I decided to put on the spare that came with my '99 GMC truck, just to see how it fit. It's also a 6 x 5.5" bolt pattern, and it fit fine. That's when I noticed the center hole...

Turns out the spare from the newer truck fit the hub on the rotor perfectly, but the stock wheels on my '69 have a larger center hole (something around 3.5 inches, compared to the ~3.0 inch hub on the rotor). Below is a pic of the stock wheel on the new rotor so you know what I mean...


You can see that there's a fair amount of space around the hub, and only the lugs/nuts would be taking the load. My concern is that if I buy aftermarket 6lug wheels, they'd also have the smaller center hole, and I would not be able to use them on the rear end (still stock 6 lug drums). I'm a little disgruntled about this because of all the posts /websites / magazine and catalog ads out there, I can't remember ever seeing one that mentioned anything about the center hole being a different size, even when staying with a 6 lug pattern.

This brings me to my questions:

Are aftermarket 6 lug wheels generally available with both size center holes, or just the newer smaller hole?

If I convert the rear to 5 lug axles, which axles can I use to keep my same housing/differential? '69 are shorter than 71/72, right? What about 70?

Is there a difference in axle length between same year leaf vs coil rearends?

Do all 5x5" bolt patterns (wheels/drums/rotors) all have the same size center hole?

Any other options someone see out there? I like the idea of having all 4 wheels the same, so I can rotate the tires and only need one spare... This center hole business shot my previous planning all to hell!

Thanks for any info you can provide!