1978 280Z electrical gremlins

All you need then is the resistance coefficient of the wire used to figure its resistance and probably the current rating.

My car has 2 red,1 brown and 1 black (plus 1 black foir the e.f.i. system)

It would help me to know what the current ratings were so I can put the right one on the right subsection, although I could just go with what the book says to use.