You should really look into the Holley/Weber that Tom Langdon sells. It's probably the most affordable option. You're looking at MAYBE $150 for a new/refurbished carb, linkage, and adapter. You'll spend at least that much for any carb at your FLAPS, then you'll still need to figure out how to mount it and hook it up.
I got the H/W from Langdon's, and am happy with it's out-of-the-box, no-fuss operation on my stock '59 235.
I think I've read that there are better adapters for a similar price out there.
Alternatively,
http://www.rockauto.com/catalog/x,carcode,1121285,parttype,5904 Good luck!
