Basically you will be swapping out the boards DB9 port with a new FTDI USB converter. radios that this will ideal for are the Icom PCR line of receivers and the Ten-Tec or any radio that has a standard DB9 Serial port.
RX-320D receiver with a standard DB9 Port
Icom PCR-100 receiver with a standard DB9 Port
Digikey and uses the standard FTDI chipset & drivers that are supported across all operating systems, Going this route will minimize driver headaches vs finding a solid/functioning USB to Serial converter.