I drove a rig that was a lot like that in Denver. For a bit, I was sure it was the same rig. It'll benefit greatly from a bolt on super charger. The c6 is extremely tough, but a 3 speed. Highway speeds will be at high RPMs. It's not that big of a deal, but something a buyer might want to know about. And of course, being an ambulance, even with the extremely low mileage, it might have a lot of idle hours on the engine.
I test drove an ambulance once, but it was a box style and super, super heavy. This one looks like it might come in at or under an SMB. AFIK, there should be an hour meter under the hood. If it's been removed I'd seriously question the motives of the seller.