dodge at4 dating

just looked in my at4 parts book and By the engine number it is either a 1965 at4 329 or a 1965 at4 353

Any clues on the following number??

AT4 - 329-61/ BF23 2421

AT4 329 ( 3tonne w 129" wheelbase....ok, prod number 2421.......ok)

What about the " -61/" ? (Door Tag starts with " 6/71" month & date????)

What about the "BF23" ??

Cheers,....

bf23
First letter = A 1970 B 1971 C1972 D1973 and so on
2nd letter= A January, B feb, C mar, D april, E may F jun
number = day of the month
so BF23 = 1971 jun 23rd production complete date