[special-K]

You have the vertical rectangle with simulated vents and Custom script on top? That's the top of the line equivalent to a Chevy CST. It's actually a Super Custom. Customs had a Custom script-only in that spot. It's larger and a little different than what you see on doors. I guess you have the buddy bucket seats,a horn button with clear plastic,and all the trim. Sounds like a nice truck from factory. I'm guessing the 327 was put in,unless there's something I never knew or saw. I'd think a VIN wouldn't vary from any standards. It's the whole basis of what identifies the truck for the owner,dealer,MVA,and anyone who services it. The engine towers,what the motor mounts bolt to,would be different for V6 and V8. Those could also be swapped,but most never did when swapping motors. I'm not sure,without looking at your truck,of any ways to tell. I assume your option sheet isn't on the inside of the glovebox door.Very few '67 GMCs got those...for whatever reason.