My oil bath air cleaner is somewhat different than the one pictured in the service manual, in that it only has two pieces. The filter element and cover are one piece and the lower pan where the oil goes is the second piece. There's no separate cover like is shown in the service manual. I didn't realize there should be a gasket between the two halves, so after reading this thread and Woodcmiami's post, went out and made one with some paper gasket material. Looking at the carb to air cleaner joint, I'm thinking of getting a 2-1/16" dia o-ring and using that there.
Looking at the 55.2 Truck Service Manual I have, it shows what looks like a 2-piece air filter that was standard on big bolts and optional on other trucks. Can't tell if the cover comes off of that by the picture. It may be what I have.