500 cfm carter afb WIW

I usually don't ask these kinds of questions because I like to do my own research but I really can't find what I'm looking for. I recently picked up what appears to be a 500 cfm carter afb carb that I figured was a 625 like all the rest. Well it turns out this one is not, its in pretty good shape, guy said he just took it off a dual quad set up but I don't think it is a purpose built one for a dual carb package. I was wondering if you were to sell something like this, how much would you let it go for?