The corrected boards have now been ordered. I was able to add the L Line using the RTS line of the Serial Data Bus Interface. I also was able to add a duplicate K Line using the DTR Line. I added the duplicate K Line because it will be impossible to get the normal Tx Serial UART to go down to the 5 baud wake up necessary for initialization of the ISO protocol. So the second K line will be used to pragmatically perform the 5 baud wake up sequence and then go quiet when the normal 10400 communications commence with the standard Tx UART.
Although…, if memory serves me, it is possible to emulate the slow 5 baud wake up using a higher more obtainable UART speed, like 9600 or 10400, using a manual bit-bang method. But I am not sure if I have access to this type of control with the UART chip that I am using. I will have to go digging through my notes. But now at least I have a secondary K Line in case I can not get the slow init to operate as designed through the normal Tx line. More flexibility through redundancy is usually never a bad thing.