Dating pumps goes like this: 1965 rebuild-able pumps have a part number followed by 2 letters. 1st letter is month,2nd is year.An example would be : 4657KE (Nov. 1965) 1965 ended in E, 66=F
Crimped pumps were phased in around mid-year (June)1966. At this time the 2 letter dating preceded part#(at beginning). An example would be: GF40433 (July 1966) for 67 model year car. 2nd letter is year where: F=1966,G=67',H=68',I=69',J=70'. The months, 1st letter, are A-L=Jan-Dec. Starting in 1971 a new Julian alpha/numeric dating was used. An example :219K40956 (219th day of 1971)This would be for a 1972 car as this is late in the year, but shows that dates follow calendar and not model year. K=1971 remembering this includes 1972 models up to Dec 1971. L=72 and so-forth. Hawks pump is: 343K40727. The 343 is 343rd day of K=1971 (Dec 1971),which is late in year and considered a 1972 pump by model year production.