[tubman]

To re-iterate: The carb must be a small base version (the large base versions are just enough different so they don't fit.) The Chevrolet carburetors have a side mounted fuel inlet, and the throttle and fuel lines will almost fall into place if the carb is mounted backwards. Trust me, it doesn't know the difference. I have several of these setups and they all have automatic chokes. If you match the choke type and carburetor choke types, the choke systems are compatible as well. Both the Rochester carburetor and Mercury manifolds come with either divorced (mechanism on the manifold) and regular (mechanism on the carb) automatic chokes. Either takes a minor tweak of the actuating rod or heat tube to fit. If in good shape, both are easy to adjust and work fine. I am usually a "manual choke guy", but the automatics fit so well and work so well, that I gave in.

There are a couple of other things to consider. While the small base 2G will bolt right on to the Mercury manifold, there is a mismatch in the throttle bore sizes. The carb is 1 7/16" while the manifold is 1 1/4". While the carb can be used as is, it is better to match the manifold to the carb. It can either be "bell-mouthed" or bored out all the way down (the method I use). There is plenty of "meat" in the casting as I have never had a problem. I have done both cast iron and aluminum manifolds and both cut easily. Also, there are heat channels in the base of the 2G that can cause vacuum leaks. I make a 1/16" aluminum plate that sandwiches between the Merc and Chevrolet gaskets that solves this problem.