I have used dual Rochester carburetors on a 1960 261 engine. It was not a good "match" - "too much carburetors".

It had a rough idle and poor acceleration at low RPM.
It had nice acceleration and power at high RPM.

http://www.1954advance-design.com/media/261RIGHT.jpg
http://www.1954advance-design.com/media/261LEFT.jpg