Like the previous poster, I don't see how this could work. If the SYNC byte isn't received correctly, how does the receiver fix itself? This is plain serial data, I can't send just 2 or 4 bits at a time.
Or is the idea that you send 4 bytes with the data in the middle and then the receiver selects 8 bits from the middle so that the edges line up....?
I can do something like that if someone says it is indeed necessary. However, the tutorial (http://www.sparkfun.com/datasheets/RF/KLP_Walkthrough.pdf, page 3) doesn't show anything so complex. Neither do any other sites that talk about these units.
In fact, the one you link to says this: "...receiver likes adjust its input gain depending on input signal level. First byte tunes receiver to accept normal signal after then address byte, data and checksum can be read more reliably." That doesn't sound like a syncing so much as a "there's some data coming, so wake up!" byte.