56plaza

Hi guys, I have query for the old timers out there. I have 3 Canadian 230 cu. in. flat head engines (25" block) and would like to verify what the serial numbers indicate. One is out of a 1955 Plymouth (# P26 1805 OC). That one is pretty much standard and straight forward. However my 56 Plaza 's # R60 126965 and my 40 Fargo's # R12 6810 are no normal serial numbers. I know the 1956 engine is a factory rebuild, so I assume the same is true for the 1940 engine (hence the "R" prefix). What I can't figure out is what size the 1940 engine is (a 201, a 218, or a 230). All I have to go by is serial numbers. Any ideas. Thx