SeaFoam isn't too bad but I've had better luck with Gumout Tune-Up with PEA.
PEA means 'PolyEther-Amine' which is a potent Nitrogen based detergent cleaner, that will attack deposits better than SeaFoam does. It is like what you find in Shell gasoline, V-Power with Nitrogen, their Premium grade gasoline. Great stuff. Run a few tanks full Shell V-Power thru your everyday driver it really scours the injectors clean and burns off carbon deposits and gunk.
Has to be good for a Model A too just haven't tried it in the A yet
Check out their web site it explains the science behind it.
https://gumout.com/our-ingredients/