Yes, there was a slightly bigger Rochester carb on the 261. Like a lot of other 261 stuff, they're hard to find, and after 60-something years, anything you do locate will have been worn out and rebuilt, possibly more than once. If a 2-barrel carb of any kind is used with an original stovebolt intake manifold, an adapter must be used. That reduces the efficiency of the intake system pretty severely. It's possible to modify an intake to use a 2 barrel properly, but it's a complicated procedure involving machining and welding.
One option for the 261 would be to find a Carter YF carburetor for a 258 cubic inch AMC/Jeep inline six. It is a bolt-on swap to a stovebolt 1 barrel intake, with only a little tinkering with the fuel line routing and throttle linkage. It's also 30-something years' newer production. RUN- - - -do not walk away from the "new" carburetors that claim to be Carter YF clones- - - -they're made overseas and the quality control sucks like a vacuum cleaner!
Jerry
