I looked in the Hollander Interchange and it shows 51-53 pass 8 cyl automatic, 52-53 pass 6 cyl overhead, 52 truck 6 cyl overhead, 50-53 Merc automatic.
Starter catalog shows #3108 5 3/16" shaft ( which I think is the short one) one mounting ear. See link for picture.
http://www.wilsonautoelectric.com/Pa...7-e690abfc15fd
Bob