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!

[pissonNOS]

is this a problem because you got oversized brakes or something? seem ive seen other trucks with drop spindles and 15" rims no?

[68shortfleet]

The wheel hub bore on your 99 in the standard size GM change to starting in 1988 on all of their 6 lug trucks. Most of the aftermarket wheels will be available in this hub bore size( GM hub centric ). And usually will be available in the larger bore size also. Hub centric wheels from the factory were not very common until the 80's. Yes the hub centric wheels help carry the load, but they also seem to balance and run down the road way smoother. Most aftermarket wheel in the 5x5 pattern will not be hub centric.
HTH
Jason