Looks like I was able to answer my own question, the PDS the PCMCIA module hooks into is 16-bit @ ~16 Mhz, so it has a maximum transfer rate of ~32MB/s, not including latency, overhead, etc... which is more than even the fastest PCMCIA 2.1 PC Card mode rate of 20 MB/s, so the limiting factor will mainly be the PCMCIA transfer rate, as long as I get a card that is 20 MB/s or faster.

I am looking forward to testing how fast the PCMCIA transfer rate really is with some benchmark programs.