As previously stated, NAPCO wasn't used on the light duty trucks after 1959 except for some 1 ton conversions since GM didn't offer a factory 4x4 1 ton (k30) till the mid to late '70's ('77 I think).
From what I've seen, NAPCO continued upfitting GM medium duty trucks into the '70's and possibly early '80's well after the light duty days were over.
Amazing truck by the way. You should sell it to me
