All the 500 and 550s to 1976 and the 77 550F had the same carb bodies, hard to tell from the outside except the stamp as calj says. It's the set up on the inside that's important. Jet size, needle clip position, etc. Frankly you will have trouble with any pods on any of these carbs if you want the bike to run dependably.
I would say the richest running carbs will be the 550K model 022A set up.