It's 6 pins in one row; power, ground, data, busy, and..two other things that aren't important. The 3900 is 7 or 8 wide, because there's an extra pin for the display to send stuff to you. It also requires a special connector that I got from digikey to attach, you can't just stick a hard drive ribbon cable in (the pins match, but it has a socket around it).

So they're not going to be pin-compatible with Mike's board), but one could always make new ribbon cables.