fuel vent lines inside cab?

[suspect]

i noticed in LakeAnna's build thread that he was asking what these lines were for. VA72C10 said they are fuel vent lines that came only on the 72.
hopefully VA72C10 will see this and give me more information.

i have a 69 c10 and i have these vent lines. my title says 1969. however, i don't have a vin on the dash in the windshield. the only place where i have a vin is on a name plate that's rivited on the drivers door jam. i suppose it's possible someone swapped name plates.

what are some other ways to distinguish a year? other than a front clip.

thanks.