I don't know if there different from BB/SB, but I think each year mounts a little different.
I have never seen them reproduced.
Ricks 1stgen advertises them as used, but when they get them, they don't last long, so you have to call.
I've also seen them at American Graffiti in Denver, but I know they have been restoring several 'verts, not sure if they are for sale.
I do have see shakers on
ebay once in a while, 4 auctions today..
They ussually sell for about $200 for rear pair, and $400 for front pair.
(apparently the front get's hit twice as often as the rear)..