The internet search is a friend.............
You threw me a curve saying "10 bolt". In GM speak that usually refers to the rear ends that started production in '65 and went on for a couple decades. It refers to the 10 bolts that hold on the back cover of the differential housing. Your '55 originally has an enclosed/welded housing with a drop in carrier (the "pumpkin"), which is probably where you got those numbers, though they might have 10 bolts holding the carrier in, they're not what most people mean when they say "10 bolt", at least in GM rear end speak.

All that out of the way, looks like the BB decodes to a 3.36 ratio. But as suggested above, over the years changes could happen so it's worth a manual check.