I have seen a couple in pickups, but mostly in medium duty trucks. But it seems like the Corvette's may have had that also? Did you loose the original fitting? There are a couple on this page, but since they are stainless they are spendy.
http://www.summitracing.com/search/P...nless+fittings
You could just eliminate the riser under the thermostat housing, and plug the port in top of the water pump, and be just fine. That is how most engines are.