Yours should have been the 6-bolt spindles Chris. All the pre-disc Ford Dana axles used six, while the disc brake Ford axles got the 5-bolt spindles with the larger flange.
I guess that's why we don't see too many 5-bolt ready spindle shims around. Since Ford was apparently the only game in town for that particular size, the aftermarket didn't just jump all over it.
They're still out there though. Someone was finding them at Napa or somewhere as a special order item.
They can be in plastic or aluminum or steel, with the metal ones being a little more desirable. But there doesn't seem to be any real negatives to the plastic unless you're really hard on your stuff. I would say that if you have larger than 35" tires though, maybe stick with steel or aluminum. If you can find them.
Paul