Yes, I would say 3.55 is plenty for a 2.7. Not sure if I would personally go lower than that if I were towing often or heavy loads, but you should definitely not limit it to 3.73.
Also, regarding brake controllers: You can get a factory unit installed cheap. It's already prewired. Just get...
Take what mechanics say with a grain of salt. They have their bias just like the rest of us. Also remember that V8's made up only about 25% of all F150 sales, so the shops see more ecoboosts naturally. Any of the engines should serve you just fine. Main advantage of 5.0 and 3.5 is the higher...
Oh, I'm sure it'll be a rocket. That engine in a Supercrew is already a monster. But in a "work truck", I'd rather save up front and get slightly better mileage (mostly because I won't be tempted to go into boost!) :D
You could even do better than $36k
And that's a supercrew. Supercab would be slightly cheaper...
I've seen some shady dealers spray pretty much the whole underside with black spray paint. It's very obvious, but maybe not to most buyers. The dealer you're buying from seems to have good reviews, though.
Good luck. Take I70 back and hit some national parks along the way.
There are lots of dealers with these Canadian trucks. Even small ones. I'm assuming there is a huge importer selling them at auctions. I haven't seen any new vehicles, though (not sure if you are asking about new or used)--all are used.
As mentioned before, check the Carfax. If this is the same truck you're looking at, it's from Canada. Lots of (rusty) trucks coming to the states from up there. Granted it's only now ~1.5 years old, I wouldn't touch one, personally. The carfax link is right on the dealer site.