That probably won't work very well... PCMCIA was not designed for that kind of cable length; IIRC. I've only ever seen it directly attached to a PCB (either the motherboard of a laptop or PDA... yeah, remember those? ...or a PCI card). I suspect that unless properly terminated, you will get signal reflections, timing issues, and possibly noise on the lines going to the card (this is why SCSI was considered something of a "black art" to get working right; and why all modern data connections are serial... even internal ones like PCI Express - with just one line or a pair of differential lines, you can have the receiving end automatically adjust it's line termination and timing isn't an issue because because it's only a single channel, not 8 or more that all have to arrive at the same time).
The physical hardware is still available (connectors, etc); and it might be possible to construct an adapter that had a PCMCIA card interface on one side; and a SPI connection to a SD card on the other end (that cable length is routinely seen on 3D printers, so I do know it works). However, this would be a substantial engineering effort; I suspect that at the least a CPLD (but a full FPGA might be required) and a reasonably fast microcontroller would be needed.