When these carbs are allowed to have water stand in them for any significant amount of time, the carb bodies corrode where the main jet is captured. It's the protruding post into the carb bowl. With enough corrosion, the oring for the jet won't seal and the carb will never function properly. I have a set where this has happened. Unfortuneatly, the well drain at the gas cap on this model can plug and fill with rainwater. As the caps are vented, this allows water to enter the tank and carbs.
White powder is usually aluminum corrosion. A Light dusting is okay. But, usually "light" is a different concept between buyer and seller. Even severe fuel deposits are cleanable, but lost metal to corrosion isn't acceptable.
There is a fuel tube that feeds a T between 1&2 and 3&4 carbs. Some 550s have a single fuel petcock outlet with an additional T for distribution and other 550s have a dual outlet fuel petcock.
All the carbs you pictured will physically fit onto your bike. If the seller won't tell you the set up number of the carbs, don't pay over 20 bucks for them. If you can verify they are for your bike, and pics of the main jet posts show good base metal is present, they should work and you should pay what you can afford. Be prepared to replace all the rubber bits in the carbs regardless of what you buy. Honda sells a rebuild kit with all you need for about $18 per carb.
I've never paid more than $40 for a 550 carb bank. And, about 8 months ago I bought one off eBay for $10 + shipping 'cause no one bid against me. They were F models, too.
I'd pay $100 for a set of carbs, but they'd better be primo, and me desparate.
Cheers,
