I am not too sure what kind of swap you are doing, so here are my best guesses. Big block and small block distributors are interchangeable, so that is not a big factor. If you are interested in the electronic distributors made by GM (HEI) , you will need to get one from 1975 to 1984. The later ones require a computer connection, which is not a good idea. The computer HEI will not have a vacuum advance can, so it is easy to identify.