Another modeler at the show guessed it as a '63 as well, so I'm calling it a verdict.

The blue-gray is a bit of a twist, the pickups were not common even in the day, and I don't recall ever seeing that color plastic in a box or built.

And, whilst plumbing the depths of my '62 builder box, I found the Modelhaus GMC conversion... hehehehe. And that V6 is out there in 3D....

Was pleasantly surprised to find that parts from the '72 LWB are darn near a drop fit (!)