So after a lot of googling, reading S12 and Z31 forums, staring at wiring diagrams and dissecting my old ignition module I think I may have a solution to my module wiring dilemma. I am left with a wire on the module that is the "negative" or "emitter" side of the module though. It seems that on Z's etc it does eventually ground, but goes through a series of plugs (and possibly the ECU too) before grounding.
Am I missing something obvious here, or should I just go ahead and earth this bad-boy directly to the chassis? Thanks.