Just seen these after some time away from the forum. Really great stuff.
A while ago I actually had my eye on using the Artizan KKBB security guards for some sort of Ghostbusters conversion project, but in the end nothing came of it. Perhaps this was the inspiration I need?
The Cadillac ambulances you see on eBay are apparently 1/64 scale (I even got around to emailing a seller, so close was I to kickstarting the project), so might do nicely for Ecto-1.
Cheers!