Sorry for the double post. Here is a picture of a bracket on a 69 Firebird M21. I think Matt is right about all 69 Camaro Small Blocks, at least with a Muncie. I imagine that is also true for all 68-9 Firebirds with a Muncie as well.
As far as value goes, I'm not too sure. They used to be very valuable. Recently reproductions came out so I don't know where the value is at this point. I'm sure it is still worth a pretty penny.
Jason