Jimm 8/30/2011You may realize a slight increase in fuel mileage - due to the smaller secondary venturis on the four-barrel carburetor versus the two-barrel. There are several cost-effective improvements you may also consider; tuning with seat-of-the-pants timing method (try advancing the distributor base timing just far enough with the highest vacuum gage reading at idle, and the vacuum advance disconnected) just before the engines starts to 'ping'. Changing the rear axle ratio to a lower numeric ratio; i.e from 3.50:1 to 3.00:1 or 2.80:1 as example - may help in reducing the engine RPMs at cruising speeds. You may also try; improving the exhaust (less restriction) with a more free-breathing muffler. Swap or upgrade the points ignition to a Pertronix Igniter (drop-in) electronic unit (hides under the stock dstributor cap). Upgrade the stock camshaft to an RV or higher torque-style of cam profile to give greater economy.