I'm not sure why you need this information, but you could try writing an email to Dreamworld. Their social media team is pretty active and if you're doing a blog/vlog about it, they might even have photos, videos of the ride and the demolition to share. Given their rebranding to a more classic DW aesthetic, they might still have a train and a piece of track for it to sit on - even to install as 'memorial' theming for whatever goes into the empty plot of land.
If anything of the original ride does exist, they'll likely be able to find out and might even invite you to come see it for yourself.
To be honest, if it does exist, I think DW would probably want to do this anyway to promote whatever is being built on the 'historic' site, since they'll likely want to promote it as being as iconic as the original ride - even if it's for water park expansion.