Here's the way I see it. It's a '65 or older, non-synchro low gear Saginaw. They had 4 bolts on the side cover. In '66 they went all synchro, and have 7 bolts on the cover. The casting date of L271 means December 27, 19X1. The decade is not indicated, but it wouldn't be '71, cuz that would be a syncgro unit. Most likely 1961, and put into an early 1962 model year vehicle.

Bob