I applied to Holden for letter of Authenticity which I received from Holden (thank you)

in the letter it mention's

"Sandman vehicles cannot be identified by Holden build records (VIN). Holden build records will only indicate if the vehicle was built as a Ute or Panel Van.
The owner must check the Body and Option plate for one of the following option codes (dependent on model): XU3, XX7 or XY5.
Whilst Holden takes all reasonable care to ensure the information"

understanding not all sandman's have XU3, XX7 or XY5

XX7 & XU3

XX7 Special Vehicle Package was the name designated by GM Holden to the Sandman while the XU3 Special Vehicle Package was released later in mid 1975 during the HJ series, giving GM Holden an additional Sandman model on the market.

XX7 used standard passenger vehicle tyres (10cwt).

XU3 used the standard commercial tyres, rated for load carrying (14.5cwt).

HQ and early HJ did not carry derated tyres.

The GVM of a HJ-HZ will help you establish if it could be a genuine Sandman.

What's XY5