I have contemplated an AWD Z on and off over the years. Im thinking of aquiring the parts to make it work after I get my DOHC head done.
I guess AWD would be a bit of a mis-nomer, 4WD is what it would be. Get one of the seperate transfer cases off of an early 80s 4wd nissan truck (cant remember what years exactly, but soe of them came with a seperate transfer case), then make a custom front crossmember that would include a diff mount and allow the axels to pass through to each front hub. I think youd have to notch the frame rails and re-strengthen the area at the bottom of the strut towers to get some room for suspension travvel and front axels, and the floor pan might be a bit of a hassle to clear the transfer case and driveshaft, but it sounds do-able.