Right now I just want the truck on the road. It will be a daily driver around town doing some light hauling. Both carbs were just rebuilt. So do I use the original carb on the rebuilt engine with its good exhaust, or will I gain some power with the 261's carb?
Use the original carb.
An engine, less fuel and spark, is an air pump. You can increase the air in and air out; but unless you either improve the volumetric efficiency (read camshaft and compression) or increase the maximum RPM of the engine (read lots of changes) the bigger carb and headers will add only marginal power (if any).
And I concur with Jerry. Too large a carburetor WILL RUN LEAN, as the lower air velocity will not maintain the design A/F ratio.
Jon.
