The car is taking longer to start every year.

I've replaced the fuel pump and rebuilt the carb, sealed the well plugs etc. with no change.

After cranking for 15 - 20 seconds it starts and runs fine thereafter.

Thinking the gas is evaporating since they removed the additive to prevent evaporation from fuel.

Anyone installed a little inline electric fuel pump to bring up pressure before starting?

Not evaporating overnight but maybe after a month.

I haven't installled an e/fuel pump Ron, but your problem seems odd, to me anyway. Do you really feel fuel is not getting to the carb? 

Ever disconnect the hard line from the pump-to-carb (at the carb of course) and catch it in a jar to see what you're getting? 

What type of choke does your Rochester have, and is it working properly?

Steve

Here's only a thought. What filter in the carb do you have? SOME of them with the long paper filter have a flap that is on the end in the carb. It keeps pressure in the carb itself to assist in starting.