Pictured are the mono-leaf on the left and multi-leaf on the right. The difference is the depth of the pocket.
If you are making your own housing these may be of help. They fit a 3" tube stock diameter.
These perches are common on the following:
1967 Camaro - Mono-leaf
1968-1969 Camaro Multi-leaf
1970-1981 Camaro Multi-leaf
1962-1967 Chevy II Nova Mono-leaf