Build Sheet Information

[Portland68]

Just picked up a 68 GMC today with a nice set of buckets I'll be putting into my 68 SWB, I was hoping to get some information about the build sheet before passing the truck on to the next truck nut. I see the Z84 option for a CST, this truck has "Custom" above the door handle but is it a Custom level truck or is this given to Super Customs?

Also I'm having trouble figuring out what rear end is in the truck, I see that it's a dana 60 but haven't found anything under axle code YU.

Thank you for your info!

Edit: Well it looks like my pictures uploaded sideways, I'll work on fixing them but for now there you go.