There were 3 different manifolds used for the 1956 to 1961 Corvettes and the 1956 and 1957 passenger car. The early '56 casting number ended in 725 and the late '56 ended in 394. the '57 to '61 manifold ended in 653. There isn't much difference in value of the manifold. It mostly depends on what you need for the car you are restoring. I'm not sure what the 2555 carb was used on but it was not a Corvette in either single or dual fours applications. These carbs are for a single four barrel application setting on a dual manifold. You see this a lot at swap meets as the correct carbs are hard to find and expensive. From the number I'd put them at model year '57 or maybe '58 full size passenger car. If you try to sell this as a set you will get way more people telling you that the carbs are wrong than people wanting to buy them. Most will probably just want the manifold.
From the pictures the manifold looks to be in very nice condition. I don't see the common corrosion around the thermostat housing and there are no broken bolt holes on the corners or welds. You see these advertised these days for $200. up to $400. or so, depending on what the seller values it at. I'd search on Ebay and Hemmings Motor News sites to get an idea of what the common price is. It isn't a particularly rare part but someone is always looking for a nice one.
The carbs would have some value as cores or parts carbs to a rebuilder of early carbs. They look clean. If someone needed that exact carb number then the price could go up. Again I'd search ebay and Hemmings for similar ones to get an Idea of what others are asking.
If this was a clean, complete, correctly numbered set just needing restored it could go from $2500. on up.
Tom
