Dutch Dolly,
Well, I'm not sure where your "Mechanic" is getting his info from but, as you can read, there's many happy folks out in RV land that have been running the Ford V-10 Triton engine for quite a few years. And, like any engine, it's been improved upon since conception. The earlier years, as in around '99 to around '03 or so, plus or minus, really didn't have too many problems as has been suggested. They did have a minimum amount of threads holding the spark plugs in, in comparison to other engines and designs.
The later versions not only improved that situation but, took the 275 early version to, around 365 HP on the later versions. As for the 8.1 Chevy engine, that too has been around for quite some time. It's a great engine too. That engine and trans (I forgot what normal trans comes with the 8.1) usually, in the same make and model motor home, will run down the road at quite a few less RPMs than the Ford V-10. The V-10 is a higher winding engine and, will sustain higher RPMs for a zillion miles and hours.
We had our '99 Fleetwood Bounder, a 34V, with the early Triton V-10 for over 7 years. It took us, towing Jeeps, all over the western U.S. with out any issues. It was as dependable as one can get. In that time, we only did one tune-up on it. We changed the serpentine belt once or twice. It started right up, each and every time I asked it to. It was outfitted with the Banks system just prior to us acquiring the coach. That mod, supposedly kicked up the HP to around 300 or so. All I know is, it ran flawlessly down the road, and up. It never had any heating problems or anything else for that matter.
If I were you, I'd not shy away from any nice coaches that are equipped with the F-53 chassis and, the Triton V-10. You'd be missing out on some possibly great values and, outstanding dependability. Your choice.
Scott