I've been using the silicone trick for years now. I use the regular black automotive silicone, and put it on both sides of a header gasket, and sandwich it between the header and head. I never have a leak, and the regular silicone takes the heat.
Did you search? I found these by putting your title in the search function:
http://forums.hybridz.org/showthread.php?t=113108&highlight=PILLAR+MOUNT+gauge+pod
http://forums.hybridz.org/showthread.php?t=113339&highlight=PILLAR+MOUNT+gauge+pod
First off Welcome!
I would try to fix your wiring problem first. Even if you drop in a V8, you are still going to have this wiring problem, unless you plan to rip it all out and start over ( expensive and a pain in the butt.).
As you noticed there aren't many Z31 V8 cars. I would try and email all those that you found and start asking questions
Good luck!
I was looking for inner tie rods, which are a real pain to find by the way!, I found Courtesy's site and they wanted $135.59 for the inner/outer assembly. I called a local Nissan dealer and got the same assembly for $98.50!