In my searches for a set of remanufactured Rochester B carbs, I've come across two very good resources. Both have vintage cores they are willing to re-do to your specs and both perform a complete remanufacture process down to re-plating. Both seem to be fair in pricing. Both offer limited warranties.
The first is: Jim Slaughter with Carb Junkys. He is very familiar with early GM carbs and well versed in the GM inline 6 and multi-carb set-ups. He took his time and was very willing to discuss my project and needs with me. His number is 866-961-2272. He's located in Atlanta , GA and his website is:
http://www.carbjunkys.bizThe second is: I-5 Components. I do not know much more about them aside from that they have several vintage cores in stock and are willing to bend on their pricing somewhat. They are out of Southern California and their phone number is: 1-800-526-9952.
I just thought that I would put this out there for anybody that might end up in my situation searching for good carbs. Hope it helps.