More importantly, you'll need to think about the fuel pump. With the T120 & new Speedmaster tanks, the fuel pumps are the same, so all you need to do is get a new pump/tank gasket
and you can re-use the Bobber's fuel pump. Though the fuel level sending units are different IIRC. With any other tank, you'd need to look into that.
By Grabthar's Hammer... what a savings.