during the 1951 model year and continuing into 1955, the 226 came with Auto-Lite A7 plugs. A-5 plugs were put in all earlier cars and was the factory suggested alternative for cars having heating/vapor lock problems if they had A-7 in them. There is a slight drop in mileage but the car runs a bit cooler (A-7 is higher heat range).
As an alternative on the road, you can use the J8C (which might have an issue depending on length of plug wiring), an AC 44 or AC 45, Auto lite AR51or A82.
Plug type is 14mm with a heat range at or just a blt below the J8C.