I was out surfing and found this:
JULIAN DATE SYSTEM
#917.254810 917 = source. 254820 = model
serial number 0521B01538
052 represents the day of year
1 last digit of year
B plant code
1538 number of unit made
So the second FF tractor I bought was made on the 52nd day of 1981 (Feb 21, 1981) and was unit # 1538. The first FF was made on the 153rd day of 1981 (June 2, 1981) and was unit # 2731.
Just looked up the GTV, and it's serial reads 0282S03265. So it is a 1982, born on Jan. 28th.