PMP 450i SM Sync

The cable from the 900 MHz 450 SM (keep in mind this is actually a 450 board, not 450i) to the 450i AP is the same cable Chris references in his first link:  This one

Just replace the "UGPS" with the "900 MHz 450 SM"... also, in this case, you'll only need the GPS/Ground pins, as you don't need power or GPS data information.