In the tech for the brakes on IH8MUD.COM Mike Smythe use's:

Pep Boy's part # for the Raybestos master cylinder I got is 20-1905 and it said it replaces RMC39570.

Off a 87 S-10

Last nite I ended up doing a master cylinder/booster swap using a master and a booster of what we thought was out of a chevy van ( was sitting on the parts shelf for quite a while and we are not sure what it was parted out of... For sure it is Chevy) ;D

Needless to say after everything was done and fabbed up, the rear part of the master is shot and I need a new one.

The one I have looks exactly like Mikes, with the exception that the lines come out the pass side of the master, vers's the driver side of the master. Anyone have any idea what that could of been out of?

Casting #'s are as Follows

846FD 1 1 8006814 with a big C at the booster side.

I tried the local GM dealer and the parts store and neither could help.

Thanks

Just got off the phone with my buddie, he said possibly out of a camaro... Anyone know if the brake lines come out the Pass side for a camaro?

It isn't a S-10, and it isn't a Vette.... nor a truck... that's all I can help on...

Found it, It came off of a 84 camaro with disks in front, drums in back.

I ended up getting a master from a Pontiac 88 GTA Trans am w/disk brakes. (Looks the same as the one from the 84) Definate improvement to what I had before. Still have some bleeding to do, but it locks up the 1 of the 39's now :D

Installation was a breeze and everything fit in nice, with only 4 holes to drill for the booster mount.

what is your axle setup?