Jerry,
Your block casting is from 1958. Your block date code is late in the year, 1957, which usually means that it was placed in the next model year. By Nov. 1957 the 1958 vehicles were on the showroom floor.
Also, this 1958, 261 casting # has been questioned a number of times. The # 3 and the #8 is sometimes difficult to read. Some say it is,
3738813
3788813
3733813
What we know is that the last 3 digits are 813.
Would you be kind enough to recheck your number, so we all can learn the correct # for a 1958, 261.
There is also a stamped number on the pad to the rear of the distributor. Can you post that info. Should be something like F106J. This will tell you the assembly plant, month and day, and the truck series number.
