maybe i should change to p89c61x2 and get another 10 bit a/d converter
If I were to select, I would go for P89C66x or P89C51Rx2.
www.maxim-ic.com has a lot of a/d converters 1-8 channels.
staying with the '552 and adding an external UART
I am not familiar with the one mentioned above, but Philips has a line of 1-4 UARTs with FIFOs for both xmit and recv. The FIFOs may come in handy since you want 115k.

Erik