avs air fuel adjustment screw
Tony, on the carb, you've gotten good answers. That one and only screw is an adjustable airbleed for the carb. I'd skip the OE AVS if ya can. There not to flexable without a reworking. The new Edel. AVS is a little better, but the Holley is best.
On the rocker ratio, you should know the cam lift at the lobe and then multiply it by the rocker ratio.
Or, if your cam is a .477 lift and want to change to a higher ratio, then it looks like this;
.477 / 1.5 = .318 (Lobe lift.)
.318 X 1.6 (New rocker ratio) = .5088 (New, in theroy lift at the valve)
Most sellers of cams want you to have a adjustable rocker to adjust for excellent contact patch on the rockers tip to valve stem for optimum geometry.