You could check for black door handles and the smaller spare wheel winch cup to suit GTS wheels but given its history, the plain colour, and the normal GVM, you'd have a hard time convincing potential buyers that it was a genuine Sandman.

Do it up how you want to, as long as you're doing it for your enjoyment. A nice van will still pull good money, and even if it was a Sandman it's hard to make money by restoring it.