Hello Chet,
I suppose you would like to use MPC574xG/C. For this microcontroller I found following:
Maximum frequency is 160MHz = F160, F80 is half of F160 and F40 is half of F80. So if you set F160 fast enough, it should be able to have UART baud rate 10Mbps.
If you have any other questions, please feel free to write me back.
Regards,
Martin