There aren't too many standard 60" long tanks on the market. A few acrylic builders offer 60" tanks, but the only non-custom 60" glass tank I know of is Perfecto's 120XH (60"x18"x26"). Oceanic used to build a 110 (60"x18"x24"), but those can only be found used.
A 60" long custom tank might be a good option. I picked up a 150 gallon tank (60"x24"x25") from Glasscages for a very nice price (unfortunately, I'm being forced to sell it, but that's a whole 'nother story).