Sorry, I just noticed you mentioned 1238 behind the starter...could that be L238? If so, it was made Dec 23 1958 which would be for the 1959 model year
With a build date of Dec 23rd (F1223B), it's unlikely it was machined and assembled on the same day you're saying it was cast.
Could the cast date be Dec 3, 1958 (1238)?
Pictures would help...

Welcome to Stovebolt

Mike B
