Hmmmmm......I thought that the EVAP went on when they removed the vented cap on fuel tanks. Doing some Googling, it looks like 50 state EVAP was in 1971. Without an EVAP canister, how did a non-vented gas tank work then? Is there a pressure valve on it?
I don't know how you retrofit an EVAP on an older carb? The factory EVAP hooks to the Monojet fuel bowl and fuel tank to passively capture fuel vapor. It runs timed (or ported) vacuum to the temp valve on the water neck which it shares with the EGR. Once the engine is warmed up, it allows the vapor in the EVAP canister to be drawn in through the manifold port that is shared with the hose to the PCV valve. I presume the older carbs (like the non-emissions aftermarket carbs) have fuel bowls with open vents, so you can't hook the EVAP hose to the carb?
