If anything, the dual carb setup will make the problem worse, not better. The only place you'll gain any improvement will be at maximum RPM, and once the engine lugs down, even a little bit, the power will simply evaporate. If you want a little more carburetor, you might consider going to a 2-barrel Rochester like the one that was used on a 265 or 283 V-8. (Not the bigger 2GC model used on Pontiac engines, Chevy 350's, etc.) Even that one would require some major machining and welding to the manifold for a proper-sized flange to eliminate the choke point that would be created by using an adapter plate.
Bottom line- - - - -pick a gear that lets you pull the load without downshifting any further, and keep the RPM's up near the maximum horsepower point. That's probably close to 4,000 RPM, maybe a little less. If you can stay at the max-HP engine speed without losing road speed, that's all the performance you're going to get, regardless of the carburetion you have. Any more power will require a bigger engine (261), more compression, or a camshaft that's able to produce more bottom-end torque.
Jerry
