where is all the SBP mags at?

Good luck finding 15's in the SBP. I looked for years and finally found some locally. They were 15X8 Western style 5 hole, Shelby brand (?) and were custom drilled for a Duster's 5 on 4 at the factory. Didnt fit my 65 after all that. Cleaned up factory new looking with a scothbrite drum on a drill. I flipped them and had NO trouble selling them.