Nope. If you were shagging someone who worked at the RTA they might look up the number and see if it's still registered. Then they'd get found out and fired cause they're not supposed to do that..

That chassis was pulled out over 20 years ago for an unknown reason, most likely damaged. It could be anywhere by now or could have been cut up or scrapped at the time. You'd have to have an insane amount of luck to find that thing now. Any records the police had showing why the chassis were changed are unlikely to have been transferred to a computer database, and chances (slim) are even if they could find that record they wouldn't tell you who owned the vehicle or did the work at the time.

Seriously, buy a better example. A panelbeater is going to charge you more than the cost of a good example just to repair yours, then there's the extra value a matching chassis will give it when finished. Your van is best suited to someone who is bloody good at welding and can do it all on the cheap. Otherwise it's likely to end up as one of those eBay unfinished projects that sells for about a quarter of what has been spent on it so far.