I had a 1966 Barracuda that had a vacuum gauge instead of a tach. It was great for squeezing the best gas mileage out of the car. It was labeled "Power and Economy" on each side of the face.
I use this method to set the mixture screws at idle but on my Rochester Quad there is only one vacuum available and I'm not sure if its a ported vac or a manifold vac. I have to look at it closer.
I had a 1966 Barracuda that had a vacuum gauge instead of a tach. It was great for squeezing the best gas mileage out of the car. It was labeled "Power and Economy" on each side of the face.