Also, originally I thought this might be a 1500 series when looking at the pictures but when I saw it in person I knew it had to be a bigger model. The frame alone screams 2ton+ looks like two freaking I-beams underneath. Plus the dual rear axel.

I may try sending an email or phone call over to GM, maybe they can help clarify?
Though I doubt they give 2 plops about an old '65 truck that wasn't part of a computerized vin system.