After some time I find a method to discover the Radio password for GM/GP 300 series (Try with GP380 and GP388R).
1. Connect the radio to the PC
2. Download a serial port sniffer (like portmon.exe) and start it
3. Push Read Radio on CPS interface
4. Return to the sniffer and find (around line 230-240) a line like this one (the last part of the line is always FF FF 00 00 00 00 00 00 00 )
233 0.04440711 gp300.exe IRP_MJ_READ Serial2 SUCCESS Length 36: 00 02 C0 32 41 30 31 30 39 03 19 CD FF FF 00 00 00 00 00 00 00
5. Take the 4 digits hex number before the last third. In this case 03 19 CD are the last third (before FF FF ...)
6. The password was 3039 in hex.
7. Find a hex-dec converter and convert 3039
8. Great: the password is 12345
Good hack
