I have a 1970 el camino, front disc brakes, and a big block. I had some replace the mastrer cylinder last year and it didn't look like the one that was in there. Looking on at The El Camino Store and Ground Up there seems to be different types and I don't know which is the correct for my car or the part number. I need to replace this one as it has actually been leaking since it was installed! Thanks

Any ideas?

70s usually had the more square looking master with bleeders right on the master. I have seen some with the more oval shaped master with out the bleeders, like my 70, which is an early November 1969 build. It could have been switched out but it seemed like the original.

thanks for the information.

The correct one is rectangle in shape with bleeders. Casting number for 70 big block ends in 409. There is a small machined surface on the front that will also have "BB" stamped into it.