GMC Vin number decode

[rstewart09]

This is my first post but been lurking here for a while and got a lot of great info. I just bought a GMC 3/4 ton with vin # CM2590DZC2392B I know this is a 1967 because it has the small rear window, but the title says its a 1969. I am guessing somewhere along the line someone just made a mistake typing up the title. I havent got it changed to my name yet and wonder what kind of trouble this will be. Looking at others that have been decoded here I believe its shows a long bed 3/4 ton 1967 but dont know what the M is as far as engine or the Z for plant. Thanks for info.