Not knowing for sure about what you have got, I'd guess you have a 60 gallon tank that might be between 14 1/2" to 15 3/4" deep.
A couple of types Moeller makes would be the one for a tank depth of 13" (MOE 03576410) or the one for a tank depth of 15" (MOE 03576510).
I'd remove the sender, measure the tank depth and go from there to be sure.
Look at this site, it should narrow it down.
http://www.jamestowndistributors.com...ogleaffiliate=
Chances are, the 15" may work.