If I am reading the date code correctly:

6= 1956
L= November
29= 29th day

So November 29, 1956 for the 1957 model year.

Some reference material for making your adjustments
Attachments
CAA7D8CF-B6FD-490A-9D09-3E202E21F30F.jpeg (266.21 KB, 156 downloads)


Mike