Hi Beachbum, sorry for the delayed response. As far as I've found, the only production breakdown is by model, and I can't get ahold of specific equipment breakdowns.
According to the Chevelles.com website there were 12,027 SS models made. The site that posted that info is below. I will also check some books I have to see if there's a breakdown by transmissions.
http://www.chevelles.com/elcamino/ec_total.htmI always liked those era of El Camino SS's and I've never seen one with a stick. I did come across a 79 Malibu coupe with a V6 and a 3 speed stick a long time ago at a cruise night in Chicagoland. It was a neat little thing.