I've parted a couple rusty 66s over the years, all I've seen have been BJ swing with wide 5 brakes and slightly different wide 5 wheels, vented instead of smoothies, flat hubcaps and no clips - hubcaps are held in by a few raised friction points that are part of the stamping.
All were factory 6 volt, all were 1300s from the factory, and all had different low back seats as well, that were curved on the back and more comfortable than the early square backed ones.
I know for certain that the brakes are a simple bolt on, bolt off conversion to later 4 bolt, which is probably what was done in your case. Not sure if the backing plates and bearings are different on the wide 5 ball joint drums versus the earlier K&L ones though. Simplest will be to use 66-67 parts if you want 5 bolt. We used the parts to put wide 5 wheels on a ball joint/swing 68.
Rears should be interchangeable as well, although it's been a lot of years to remember clearly. What was a curious difference with one of the 66's I parted was a strange little z-bar arrangement (sway bar?? - didn't look like it would do much if it was) that went up under the rear parcel shelf behind the seat.
The last set of them I had went to Stefan Feeg complete with the front control arms, rear backing plates, hoses etc. I'm sure they are long gone (10 years ago? 12 years ago?) but Stefan might be able to tell you if he used them, what they went on, and if it worked... The again if his memory is as bad as mine you'll be fully SOL on that count....