It all depends upon the series. In general a Kingswood is a step up in luxury level from a HOLDEN (Belmont only in HQ commercials). GMH used option codes for special vehicle packages, the most famous probably being XU1 and A9X. XX7 is one of those, and in HQ and HJ it could be optioned on Belmont/HOLDEN van and utility and on Kingswood utility (there was no HQ or HJ Kingswood van). The XX7 package was just a list of "sporty" type items added like wheels, dash, buckets, stripes. Whatever other features were standard on the base vehicle the XX7 got. So in Kingswood it got Kingswood trim, stainless moulds around the doors etc. Only bits in the way of Sandman stuff were removed eg Kingswood side strips.
When HX rocked around, a Kingswood panel van was added to the range but the Kingswood Sandman was dropped. So the level of appointments on the XX7 package was raised to include many Kingswood features as standard: trim, door switches, grille, full headlining (on van) etc are just a few plus some GTS features like grille painted black, black headlight surrounds etc. In reality if it hadn't been for the Kingswood side strips being in the road of the stripes I reckon all HX and HX Sandmans would have been Kingswoods.
Back to option packages, BO6 is the Ambulance pack available on HJ-HZ 1-tonners and vans. Basically it was a Premier package - the factory 1-tonners you see with Premier fronts, doortrims, bucket seats and GTS dashes are normally BO6. XU4 is just a code for a commercial vehicle with passenger tyres, nothing else. meaning XU4 is nothing special. You could order N66 (rally rims) on any HQ-HZ as well (except 1-tonner) either by themselves or with XU4 on utes and vans. Almost all optional components had a code, some were nothing items like B30 for carpet or M40 for trimatic auto. Others are a whole vehicle package like XW8 (HQ GTS350 sedan) or A9X.