Saddle Tan Metallic is the paint colour.
Buckskin Trim.

From what you have supplied there is nothing to say it's not a Sandman.
Confirming it is more difficult. If you had the owners manual and sales papers that would give it away for sure.
Black-Outs should help. Door Handles? (Should be Black, never chromed) Sills, around door Window Frames, Top Tailgate Window.
Mirrors should be body colour. Headlight surrounds and grill should be blacked out.

So your looking for spare wheel lift ring. Full Head Lining, Factory console mounts.
Factory decals? Evidence of?

Ben goes off evidence and Holden papers, he uses Byron for Sandman ID's for an educated opinion. If you get the green light from either you'd be pretty safe.
That said, if you can find the evidence I've suggested you'll be well on your way.