So you are essentially looking for an all-in-one prebuilt kitchen? That's a hard cookie to crumble but there are tons of them with a metal box, engine and wheels attached already.
One reason you won't see this, is a 3way refrigerator has to be built in/through an outside wall. So the cabinetry is very custom to the van and location in the van.
If you do get a 3way, make sure the venting is installed per manufacturer's recommendation. Our builder did not, and our hot weather performance suffers.
I've done a conversion from electric to gas and while the instructions are somewhat demanding, not all that hard to do. I'm just surprised there's no all-in-one module available, with or without a 3-way. That van only had a microwave which required the engine to be running to work, too.
I have an electric fridge and I much prefer it to the 3-way fridges I had in the past. It cools down faster and the 3-way fridges were all hard to light on propane and tended to blow out easily. Just a data point.
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N8SRE
1990 E-250 Sportsmobile w/ penthouse top, converted when new by SMB Texas.