I need to drive a slow (30MHz) parallel interface with ~26 pins some distance away from a FPGA, and want to avoid using 26 IOs. The idea is to use shift registers to deserialize the data at the receiver side. The lines will go over fpc cable and be driven differentially, and will be terminated on the FPGA side. So far I've found the 74LVC595 which goes up to 120MHz, but this is still a bit slow for my liking (I would prefer at least 8x serialization factor or 240MHz). Is there a faster 595 or other shift register IC? I would like to keep chips cost below $2 for the whole solution.