Which 8 3/4” SBP Drums and Hardware

Assuming it is really from an A-Body with the original 10"x 1.75" backing plates, the only new manufacture drums available are Centric #123.63044. They are out of stock at Rock Auto and Summit, but Amazon is showing them for $79.99. A little pricey, but probably includes shipping with Prime. These are Chinese made, but they're pretty nice. For a long time there were none available. These have been available off and on for the past few years. Maybe heading to unavailable again.
You can also check on FABO for good used drums. They pop up, or put up a wanted to buy ad.
Amazon.com: Centric 123.63044 Brake Drum: Automotive
Shoes, adjusters, and hardware are all available at Rock Auto and other places. As Professor Fate suggested, the '69 and up adjusters are improved over the earlier pieces.
The parking brake lever, strut and spring are not available new. Well, sometimes the spring shows up in hardware kits, but I haven't seen one lately.
Look in for sale here on FABO, ebay, etc.