It could be a number of things, one of them being a Sandman with ID plates changed.

If the ID plates are original to the body it is a HJ Holden (not Belmont - this was gone on commercials at the end of HQ) van which was optioned with a 4spd, courtesy lights and B30 comfort pack (carpet and headlining). This creates a slight dilemma as B30 on HJ is supposedly not available outside Sandman, which makes me thing the tags on yours don't belong to the body. GTS guards and dash makes this look even more so. Does it have brackets for a console?