So there is no information about these different -K and -D please?
Believe you would need a copy, hopefully a very late one from may be 68 or 69, to see variations changes which might or might not include what changed on each version such as the rating or scoring of the rubber that made up the insulator
- K might have been used in layer years or only available as a service part.
What you can go on is that the -D was used and installed in the April -May period of production in 67