Making craig radio work uk

[Andy_]

Hopefully someone knows what im on about. This is more a general usa import question, than a delorean specific one.
Spoke to someone at a clasisic car show, who uses their original usa radio, but with a box that goes between the radio and aerial. Called something like a “band shifter”.
So that even if the radio is tuned to fm 98.1 or 98.3, you can pick up 98.2. All i can find is japanese import band shifters that i assume are set for different frequencies?
If youre using an original usa radio in uk, how did you do it?
Thanks for any help