I think you stated that your carb does not have a bowl vent, so the system cannot recover the vapors after shut down there. In the information provided by 67Dart273 there is a note that only some models have the bowl vent.
I also noticed comparing 1972 evaporative controls to 1974 changes were made to eliminate the internal purge valve in the canister. This makes me think that the purge line on your carb is throttle ported, else purge could happen at idle. Later they moved back... It is my opinion, the mid 70's were not good years for emissions controls.
I recently had a significant bowl vent issue on an early Barracuda. I solved it by changing to a carb with bowl vent, added a tank vent line, and added a canister. Like you I rebuilt the original carb and that did not solve the problem. I paid close attention to float setting and even verified on the car following service manual procedures. I believe a 46 years of use, a porosity problem in the bowl casting, and volatility of modern gasoline are the root causes. By changing things I basically moved from 1966 to 1985. I am pleased with the results. Perhaps a solution is to locate a similar 1B carb in a later year, prior to feed-back (lean burn), with bowl vent, and change the carb and vapor recovery system.