The trick to overcoming the sentimental aspect is to spend that $30k on a restored Sandman first. Once it's in the garage you'll feel less attached to your current van. If I was in your situation I'd buy a nice Sandman van, take all the best bits from your current van and put them in the ute. That way you have a reasonable ute that you can park at Bunnings and use as a ute, as well as the nice genuine van that you can take for Sunday drives and go to car shows.

You have to remember that these aren't limited edition factory muscle cars. Even a Sandman is just a regular work vehicle with an options package added. Holden made as many as were ordered and while they're reasonably desirable, they're hardly scarce.