HeadlessRider, Welcome.
Actually, the America tank holds 4.4 gallons of gas. As far as I know, there isn't a larger tank available. The average range is about 140 miles. however, you'll find yourself turning the petcock to the reserve side at about a little over 100 miles.
My advice....that's a very good price for a nice low-mileage America, so get yourself the best made, the best handling "cruiser" on the market, and the coolest motorcycle you'd ever hope to purchase for a measly 5300 samoleans.

Cheers,
Dwight