There is a seller near me that buys used retired from service Ambulance's and removes the Ambo box from the chassis. He refurbishes the Ambo boxes and installs them on new chassis OR he will sell you a used Ambo box. He resells the old tired Ambo cab/chassis's from under the removed Ambo boxes to people to repurpose.
There for why not consider a different alternative:
Buy a None Ambo certified cab/chassis truck of your choice upon which an Ambo box of your choice will easily mount upon and insure that cab/chassis for what it is. A cab/chassis truck. Great way to get 4x4 on a cab/chassis or Van at a much cheaper cost that going the conversion route if 4x4 is important to you.
Buy a used removed from service Ambulance box that has been removed from an Ambulance chassis that will fit the none Ambo cab/chassis truck you have purchased.
Install ambo box on your none Ambo chassis to build your RV/Overland vehicle.
Certainly extra work however you can then get exactly the chassis you want rather than compromise on the chassis because you purchased a complete used Ambo mostly because of the Ambo box. This is certainly a much easier way to get 4x4 IF you want an Ambo box on a none VAN chassis as 4x4 Van conversions are expensive and there are lot's of 4x4 trucks upon which you can mount an Ambo box.
This is no different than buying any other cab/chassis truck and then installing a flat bed, box van or gooseneck trailer tow setup after purchase of the vehicle WITHOUT any of the issues of trying to title and register that "Former Ambulance" vehicle that you want to make into an RV/Overland vehicle.
Think about it.
In all reality it is the Ambo box that made you interested in purchasing the a used Ambo for conversion NOT the chassis upon which the Ambo box was mounted.
The "Skoolie" enthusiasts have the same problems with insurance coverage and conversion.