Looking at a used fleet truck
Includes hardened engine intake valves, valve seats, and bi-fuel manifold. Does not include CNG/LPG fuel tanks, lines, etc. Vehicle will be equipped with the standard factory gasoline fuel system.
Looking at a big (to me) truck to pull a bumper trailer. This thing almost sounds too good to be true. Very basic (hand crank windows!!) I don't know if that cng stuff is ok, bad or a good thing. I am not interested in converting, just wondering if it complicates repairs or anything. Tell me what else you think.
https://www.goldiesmotors.com/vehicle-details/2016-ford-f-250-super-duty-xl-truck-e23d9494b9e844718ef9550f7534044b#Features
= new reply since forum marked as read
Can barely handle DU and a few searches. Don't think i can manage new forums right now. Actually I probably have an account at one but same problem, really. 
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They'll put it on a rack, check out all the diagnostics, evaluate the current fluids, give it a test drive and share the results.
That way you'll have a much better idea of the value relative to the price.
Looks super clean for a 9 year old truck. Only 50K miles. New looking tires and battery. No dents or rust. The CNG sticker on the back leads me to think that it was already converted to compressed natural gas..... you might have to convert it back to standard fuel if that was your plan. I wouldn't know where/how everyday drives would get CNG.
Get a test drive, open the hood, check online about CNG to gas conversion. Good luck with it.