Oh my god. Im almost in tears. I just found this thread today and read every single post just now. I feel for you Austin, but seriously dont give up. If you think rewiring electrics is tough, it cant be tougher than redoing the entire vacuum system from an early 70s Continental, including the climate control
And man, as far as all the naysayers, geez, why so much hate for basically a cool project goal? I may be doing some kind of swap at some point, but will probably not go for an LS engine of any kind and go back to carbureted no ECM ECU etc. Yes it will be tough getting gauges to work and lights, but meh, a good driver and good maintenance is all you need, right?
I know a think of two about "lost causes" Austin. My 2004 Crown Vic Sport was totaled after some old hag cut me off, but I'm fixing that car up to be as good as brand new, costs be damned. If I can go through that (still going, injuries are slowing me down) and restore a 10 year old car that nobody here cares about you can swap that LS3 into your LS.
If you were closer and I had more time and didnt have a jacked up spine id offer to help with the wiring. It can be done, just hang in there man! I cant wait to hear what you end up doing, keep the faith alive!