Hi,
You can't use Shiftin and Shiftout like that. Both commands expects to be "in control" - both acts as the "master" - so they can't really be used the way you want.

Using RS232 as mackrackit suggests is probably your best bet. You can use either the hardware USART or the bitbanged SERIN(2)/SEROUT(2) commands with flow control to make sure PIC 1 doesn't begin sending before PIC 2 is ready.

/Henrik.