I don't know the cutoff dates, but it makes sense that the two and three connector types might have to be done differently.I popped my Door switches in and then connected the wiring from behind, tough but long pliers help, did not consider holding the button in! They are the 2 contact versions. The parking brake was too easy, adjust and plug in.
I didn't hold the button down, just prevent it from rotating with the body. That keeps the wire from twisting.
The access hole is really small. maybe in 68-9 it was made bigger?
I was able to take a peek at the connector with a mirror and small light through the access hole above.