Fumblin,
Glad to here you got her loose. Those old cast iron rings can stick pretty good.
Just to set the record straight,all 1941 through '48 216's and 235's used the 10mm plugs. Chevy went back to 14mm in 1949. The later head will swap onto the earlier '41-'48 216, this was sometimes done because of the limited range of plugs available in 10mm.
Bob
