Whatever you consider buying you will definitely want to be able to test ride it. If you feel comfortable with the bike shop and owner (you said he was a big guy too) then I would guess he could get you something decent. Maybe ask him for some recommendations and then you could run those by the other tall fellows here before plunking down your cash. I have seen a few larger sized bikes on Craigslist nothing in the 70 range but plenty of 61, 63, 65's if you are patient.
Best of luck and keep us posted. Plenty of good folks here to help.
Here's one I found that might be a good one to use as a starting point.
http://orlando.craigslist.org/bik/1175553426.html