Welcome to the Stovebolt forums.
IIRC, the long side is to the rear. A clue is the bushing on the rear is threaded, while the one on the front is smooth on the inside. Measuring the figure from the '51 Vehicle Info Kit also shows the front shorter, although that's not definitive.
Since you've just joined us, take a few minutes and post in the Welcome Centre and tell us about your truck (how you got it, etc) and about yourself as well. We also like to see pics of your truck (or your pile of parts
)
