Nick, thanks for the great info and pic! I can't make out if there is a jump seat in the front. Can you take another look at your pic. Thanks. Tim Wright in AZ owns the same car and this is a pic of the back of his car. You can see the style of the cot bar.
I am glad Mr. Wright got back to you. I actually called twice and left two voicemails hoping to see it in person when I was in town, but never heard back.
That car is gorgeous appearing - but not in its original condition. It had extensive work done, please see
https://www.professionalcar.org/owners-pride-mark-christy-366 . Particularly with the interior - it is very hard to say what is correct and what isn't. Driver's side squad bench is unusual in particular - quick review of my S&S photos can't find an example of one setup like that at the time.
thanks for the info John. Steve, great photos! An original gurney and bar set would be great if I can find one, but I wouldn't mind a Ferno 30 set if someone has one for sale.
It is not impossible to find specific items for these cars, the members of the PCS (have you joined?) have been very kind to me. A "correct" cot for when the car was put in service will not be very difficult to find, if you want it. As noted by others, it all depends on "when" you plan to restore the car to look like - as a Model 30 indeed could've been in there in the several decades the car likely saw service. I personally tend to gravitate to my vehicles looking like they were when first placed in service - being "state of the art" welcomed sights in their community, as opposed to 10-20-even 30 years later when they were sad, neglected, unwanted back-up units.
The below cot from Dan looks like a winner right off the bat. This ambulance of yours is so unique, and will get plenty of attention from ambulance enthusiasts who will know what is "right" and what isn't.
This came with one I bought. It is a early Washington. All I know about gurneys is that they have 4 wheels.

Someone here can tell you if this might be the one you need?
Yes - this is what he needs. It is missing the foot pad, but they are available out there. As mentioned, Steve Lichtman had one too.
that would be a 54. I have see a lot of Washington cots with the one bar stamped 21 one was even a 21. but now that I see what S&S used as the signature hook. I had one never knew what I had. at least it had the same big box on the release. but as I remember it was a black ball on the end. gave it to the man that owned the 53 ford turned in to a service car. Jim Russel did that in NJ that's been a few years back
The Model 21 could be converted inexpensively - at the factory or with a kit locally - to a Model 54.