Richard,
As we have been piecing together the Criterion statistics (with great help from Mr. Joe Grimes), we still have no concrete production number data, other than the 1974-76 breakdown of Miller-Meteor 3-way hearses vs. end-load hearses vs. combinations vs. ambulances. For 1974, I have yet to see a documented breakdown of how many Volunteers vs. Lifeliners vs. Criterions were built. For your displays, I suggest you use the phrase, "apporximately 50 Criterions were built..."
That said, there are several of us including Steve Loftin, Steve Lichtman, Rich Litton, Terry Lange, Dr. Roger White, Cary Livingston, and myself who have photographed (or received photos of) many Criterions over past 30+ years. Working collectively, I'm sure we could account for a good percentage of the three-year production run.
We would be happy to expand our Criterion section of northlandpcs.com by hosting a database of all known Criterions. I don't mean to hijack your project in any way, Richard. We'd be willing to work with you and others to enhance the interest in these fascinating ambulances since we already have the online presence established.
BTW, the new lettering on your car looks good!