Well, here is my nickel's worth: I have a '40 chev convertible with a modified '62 261 in it. Cam, head work, headers, forged pistons, bored .080 over, HEI ignition, etc. Anyway, I originally had a Holly Pro-Jection on it that was an early model and after fighting with it for a couple of years gave up on that. I have since talked to some who have the later units with the O2 sensors and they have been happy with them. After that, since I still had the Clifford 4 barrel manifold on the engine, I decided to try the Holly 390 and was amazed with how nice the engine ran! Another plus was having an electric choke which eliminates cable hookup. After running this setup for a few months, I was getting ready to head to Louisville for the Street Rod Nationals so asked a local Dynomometer service to make a run and do a tune check. (if you are interested, the car is in the "rides" section) They found the carb to be right on the money for my application with no jet changes needed...they did make one minor accelerator cam change. In that configuration, the engine put out 184 HP at the rear wheels at 4600 RPM. I have also built a couple of 261's for other guys and used the complete three carb setup from Tom Langdon with equally good success (plus it looks a lot cooler) Hope this helps. I haven't gotten any fuel mileage numbers from the multiple carb setups but I generally get 16 to 18 MPG on my Chevrolet.
