72 slant six upgrade

I have a stock motor and I am wanting to upgrade/improve the motor. One for better performance and 2 for better gas mileage. It has stock points which I am going to totally switch out to electronic. Then come the intake upgrade....? Without having to switch cams and do headwork.... I was going to go with the offy 4 or the Offenhauser Dual Carburetor Intake Manifolds 5041 series which runs 2 1 barrel carbs. BUT I have not had anyone give their thoughts about it. I will add headers at a later date with 2.5 pipe and an X pipe added. But for now the ignition and intake carb set up are my questions. Any thoughts???