If your car button I/O board is addressed 8, then make your crc board address 16
or 24. Set 326 to address 16-1 or 24-1. You need to wire the inputs. If you only have one relay and it has more than 1 pole maybe you can use 1 set of contacts for ccrccc and the other contact to input the buttons that are secured. Make any that you don't want secured a 010 as you said you have. This might work too.
