Thank you McDucks! But the WeatherTech mats are 2-piece for the E350. I am looking for the 1-piece solution.
Thank You to CalCruiser also. I found that link also, but the dimpled pattern was not to our liking.
If you decide to do the front cab area be aware that heat in that area from the engine and exhaust is a concern. I recommend you leave the existing carpeting in place to serve as insulation and put a rubber mat over it.
Thanks DynaDave!
After looking closely at the flooring in front, and talking with Mrs V, this does appear to be the plan of action now.
We have the full floor Ford rubber mat over the carpet and I worry about moisture under the mat, held in by the carpet, and rusting the cab floor. I don't know if that would happen but I hope to someday take out the seats, remove the mat, and tear out the carpet (I hate carpet.) My original thought was to have a bare floor and get it spray sealed like they do in truck beds. Someone suggested I check with an installer and see if they'd give me a deal if I brought the rig in when they were doing other jobs as they could use the excess goop in our cab. I haven't checked that out yet.
I went searching through many other forums about putting down the vinyl plank, and often there was HORROR stories about people trying to remove the glued on carpet... and a few tugs here and there made me think the carpet in the front of our cruiser is WELL glued on most of the floor. (Not at the very front, however)
I have experience putting on bedliner, and there was no 'excess goop' from jobs. We used what we needed out of the drum. If the drum had a small amount that would not be enough for the next job, we switched to a new one. Then once the new one was drawn down, put the remainder of the old in.
About the water being trapped... I had a HUUUUGE leak when i first got the camper that soaked the drivers side floor on a regular basis. Removing the step guard, and peeling back the carpet shows no sign of rust (WHEW!) I think the glue may protect...
So... after *actually looking closely*

at the front floor, I realized that it is going to be easier than I thought.

I am going to leave the original glued in carpet for noise and heat control. May put a radiant barrier above it for a little more heat control. and because I happen to have a roll to use.
The step wells on my cab are black plastic.

AND they cover the edge well. And there are only simple bends, no compound curves (ie:bowl shape) except for the very top under the pedals/forward of the passenger feet.

So I am topping it with this -
https://www.homedepot.com/p/Diamond-Deck-5-ft-x-9-ft-Battleship-Gray-Golf-Cart-Mat-82059/206315010?cm_mmc=Shopping%7cTHD%7cG%7c0%7cG-Pro-PLA%7c&gclid=EAIaIQobChMIrbOGl83c2AIVT57ACh2ykQ5ZEAQYAiABEgJVQ_D_BwE&gclsrc=aw.ds&dclid=CMPqlZzN3NgCFcQPgQods4AA-Q
""Great for workshops, basements, trailers, laundry rooms, mud rooms, bathrooms,
toy haulers, motor-homes and camping. Perfect whether you need a temporary or a permanent flooring solution that is tough, waterproof, durable and easy to install.""
YEAH BABY!!!
1/8 thick PVC. The areas in the front that have the slight compound curve can be easily formed with a heat gun and sandbag. IF needed, I can even solvent-weld it. Not to mention its about 12% the cost of the Ford rubber mat AND tougher. Will look tough also. Even matches the grey of the dash.
May need to 'shave' the carpet fibers off around the edges to get a good fit, but otherwise looks like a WINNER.
Sorry about no pics... had a large Honey-do list to attend to after work, then interior design meeting with Mrs V. I have to pull out some of the planking below the slide to shim up the floor for the rollers. Needs to be up ~1/4 inch. No biggie.