To work with the carburetor, I had to drill out the right side port (the one with the X).
I should mention the truck experienced some lean conditions after installation, particularly on throttle opening and I didn't get around to fixing it. Some carburetor adjustment will be required, I think.
The vehicle is now running electronic fuel injection and the problem has gone away as far as I can tell, so perhaps the Motorcraft 2150 carburetor I was using just needed some tweaking.
I was already running lean jets (#52 I think versus the #55 stock); maybe the old canister permitted less air flow than the new one. That is only an issue when ported vacuum increases to open up the purge valve. One might be able to restrict the airflow out of the new canister.