If my memory serves me correctly there was AC43, 44, 45, 46. All interchangeable, with the 43 being the coldest to the 46 being the hottest. Any good parts store can get you spark plugs for a Stovebolt 6. If you are going for a concourse restoration you can get new old stock through eBay or the automotive swap meets.🛠

Martin
'62 Chevy C-10 Stepside Shortbed (Restomod in progress)
'47 Chevy 3100 5 Window (long term project)
‘65 Chevy Biscayne (Emily)
‘39 Dodge Business Coupe (Clarence)
“I fought the law and the law won" now I are a retired one!
Support those brave men/women who stand the "Thin Blue Line"! Hug a cop!
USAF 1965-1969 Weather Observation Tech (I got paid to look at the clouds)