The Stovebolt Site Forums The Shop Area Making a Stovebolt Bed Don't know if my '51 1/2-ton AD originally had 8 or 9 (bed) boards?

51 is a split year. Some had 8 boards and some had 9 boards.
As the others said you can check your cross sills or rear cross sill to determine if it is an 8 board bed or 9 board bed.
If you are completely replacing your wood bed (cross sills and all) then you can choose! It shouldn't matter either way. But if you use existing cross sills/rear cross sills, then you need to make sure which bed it is.