Why not use the original metering rods and jets?
The formulation of gasoline has changed significantly since these carburetors were new. Federal and local smog laws have required extensive changes, particularly in the volatile components of gasoline. The current unleaded fuels are quite different than the leaded fuels for which the cars were designed 30 to 40 years ago. The current fuels are also formulated for fuel injected engines which are much less sensitive to reductions in vapor pressure than carbureted engines. Even if your carburetor and engine are like new, the current gasoline may require mixture changes. If parts of your carburetor are worn, air leakage will also change your mixture. In addition, modern oxygen sensor based fuel to air ratio gauges provide a much more accurate means of measuring the actual mixture supplied to the engine than was available at the time the cars were manufactured. This means that the mixture can be set more precisely for better fuel economy.
