Relm Mini-com MPU-32b covers from 450 to 480. There is an "A" model on Ebay right now but it only does 403 to 430. What is nice about this line is that you open it up and flip a switch then just casually put it back together and program the memory channels, offsets, and PL. Then you take it apart and flip the switch back and put the screws back on and you are ready to go.
I've not heard of any conversion of A to B and if there is there would be some happy people out there.