the deal fell through, now I have a million questions

The salesman will tell you whatever he is selling is the best on the market.
The Workhorse chassis was good (please notice the use of past tense) but the Ford chassis is good also and still producing chassis where Workhorse is not.

I know Workhorse had a large brake recall so you should verify it was done.
I would also be concerned of parts availability from a company that quit manufacturing some years ago.

Keep shopping. You'll find the right one.
Good luck and remember the shopping is half the fun!