A HQ Sandman ute or van was by all intentions a GTS van, just not called that. The concept direction was generated by John Bagshaw after meeting with various groups. The idea was GTS from the seats forward and (for the van anyway) empty in the back ready to be customised. A HQ Sandman is essentially an HQ SS ute or van, the only real differences to SS (or GTS sedan in some cases as SS was dead by the time XX7 came around) are:

The badges and stripes/blackout design.
Sandman was available on 6cyl HQ models, whereas SS and GTS was optioned on V8 models only (XV2 (SS) on 0269, XV4 (GTS) on 0469 whereas XX7 on 0170/80 and 0270/80 (plus Kingswood models)).
Trim (SS and GTS got unique trim codes, whereas Sandman used the base vehicle's trim).

Of course GTS had a few options not available on Sandman like dual exhaust and 350 engine and associated muncie or TH400 (SS incidentally had dual exhaust standard!).