Everything below relates to 67 seat belts.
I only include it to this conversation because it might help with seatbelt part number understanding.
It also seems that the part number for the front male and female are the same number.
And the rear M & F are the same number
And color does not change the part number
1966-4 and 1967-1 are for model year 67
1966-3 should be for 67
My note "2 examples - one is longer than the other" refers to two rear male belts in the same photo. Same part number and date but one is a few inches longer than the other.