Hi Vidya and Hooman,
As mention in my earlier post on 1/20, you can replace the LM96550 with the LM96551 on the TX-SDK-V2 board as long as you don't connect the +/-40V supplies. The reason you can do it is because the +/-40V supplies are built into the LM96551.
However, you can't replace the LM96551 with the LM96550 on the TX-SDK-V1 board since there is no external supplies connection for the +/-40V supplies.
Regards,
Charles