It seems like the consensus is 3841177. I got the 3893560 number from a guy selling an entire original system (front & rears drums, backing plate/shoe assembly, front knuckles and lines) from a 67 camaro, Norwood, June 67 build. You can look at the system on eBay, it is still listed with pics. He is converting to a disc brake system, front and rear. I just bought 2 rears (cn 3841177) on eBay and I'll be using those. Thanks.. dan