How different are the Roland GK-1, GK-2, GK-3 pickups and outputs?

[Mark Hammer]

I ask because I have a GK-1 that I don't really use very much.  I know that the GK-1 used a bulky 24-pin connector, while the GK-2 and GK-3 use a 13-pin standard, with a connector and cable that is much less bulky.

But, assuming that one could whip up an adaptor, or otherwise derive a 13-pin output that mimics the GK-2/3 pin assignments, could a GK-1 drive any of the various Boss V-Guitar units that anticipate a 13-pin input?  Or is the output level from the GK-1 incompatible?