Get us some pics. A few detail ones of the headlining strip, console brackets on the trans tunnel, tags inner door pillars where the courtesy light switch should be.
Chassis is HZ (hence why he said it was a 77 in the ad, was probably registered as a HZ.) that front nose cone with the cutouts still looks like a HZ Sandman nose cone to me, or someone raped a HZ GTS to get parts. Pic of the GTS dash as well.

Also, try scratching/sanding off some paint along the sills and around the door frame, see if there is any evidence of blackouts underneath.