First of all you would need the MKR-US-9 adaptor cable (available at BPS) for the 480 to work with your US. The biggest drawback with the older US is the cone is only 14° which limits your field of view. The newer US-1 has a 20° cone. Also the older US is not compatible with the dual beam feature. The newer US-1 is.
I looked into replacing my old US but am told it can't be done so I mounted my xducer that came with my Lowrance. Hope that helps.
Fair Winds and Following Seas
Bill H. PTC USN Ret
Chesapeake, Va