Good timing on this bump... After floating this idea around for 2+ years, I finally pulled the trigger on a medium duty ambulance about 2 weeks ago! Currently it's at my mechanic getting a good checking over once he gets around to it, but assuming no hidden issues I'll be putting a seriously overkill hitch capable of 2-3k of tongue weight on it here shortly.
Couldn't find anything ready made with the 2.5" or 3" tubes that didn't seem crazy overpriced even before install, but I have a good fabricator with access to lots of 1/2" plate and a plasma table who is going to whip something up for me for under $500. In my application, the weight of the hitch itself won't be an issue, so I pretty much told him to go nuts and make it bulletproof. I'll obviously let you know how it turns out, but in the meantime here's what I'm thinking I'll end up with.
Plan "A" was to keep the full width bumper with center flip up step, but the top of my step was right at 17" off the ground, which is right where the center line of my receiver tube would ideally be. Keeping it would mean needing a long extension (which is bad for many reasons) both to keep the bumper clear of the trailer in tight turns, and to get the ball out enough to drop past the step. Not to mention the trip hazard the receiver tube would be placed over the step. Would also have to relocate the license plate and light, have safety chains laying/dragging on the step... Basically in general it just turned out to be a not optimal solution. I did also consider a pintile plate flush with the back of the ambulance, which would allow me to bolt on any size receiver tube, or a pintile hitch, but the only problem it really solved was the trip hazard, so we went back to the typical receiver tube for simplicity.
What we decided on, was a 2.5" receiver tube, centered properly at 17" above the ground, and a flip up step the width of the rear doors located JUST ABOVE the receiver tube. I'll have a 3-4" more of a step up, but it alleviates all other issues. The bottom of the step can be pretty well flush with the top of the receiver tube, just flip up the step when you need to pop in a receiver connect chains and electrical, then flip the step back down over top (exposing the existing license plate) and go! If the 3-4" taller step up turns out to be too high, dump the air. Plus, the rear doors will most often be blocked by a bed, so it won't be a normal point of entry anyway, more just for loading. Only thing I'm not sure of is if the DOT will require the bumper to be mostly full width, but I'm inclined to roll the dice and add some "wings" around the flip up step later if need be.
Haven't really made a post about the purchase yet, but TLDR its a single owner fire dept owned 2002 International 4300 LP with a DT466 and a 230hp Allison 3060 with air brakes and air ride. Not doing much inside beyond adding the required to register it as an RV with the state (AC, a cooking appliance, and a refrigerator should do it), and a queen size bed for my wife and I. Has LED lights inside, some LED outside (but not the good ones), and due to no rear cabinet on the passenger side, enough room to put a bed between the side and rear doors without modification. We'll eventually pull a ~32' bumper pull with our two race cars in it.
