I found this recently: http://quadrajetparts.com/carter-carburetor-carbureter-parts-carter-thermo-quad-carburetor-parts-c-299_158.html
I have not used them so can not attest for their customer service etc.
I'm in the process of rebuilding my 273, per the guidance of Justin (1wild&crazyguy). It has the eddy performer intake and 1406. Here's the cam sheet and some head pics.
