I sorta opt for that option.I just did a bunch of searching because I thought this had popped up before, and it had.
Nobody has the answer. You'll have to figure out the wiring yourself, or use a different transmission. Or use a Novak shifter and just treat it like a clutchless manual.
See if you can find out the minimum data the trans needs to shift. If it's only RPM and throttle position (?) you might be able to run everything on the YJ harness and 4.0 ECM and steal those data points to feed the GC ecm to the trans.