[1967KaiserM715]

Speedometer 6 digit: almost all Canadian models received 6 digit, mainly because kilometres are shorter then miles, being main reading is in miles I don't believe this is a Canadian model.

Almost all the C50/60/70 trucks I have seen have a 6 digit reading. They are also more likely to have the tach gauge as well.

starting in 88 they added trip meters, but most are still 5 digit, but I have seen the rare 6 digit. 6 digit in 1991, but speedo's were electric(not cable driven)

I have not figured out with any rhyme or reason as why some are 6(rare though) and most are 5, with the above exceptions.