i know this is my first post here, but ive been modifying and racing Mustangs for years (though i've had 3 LS1 cars, so no flaming please!). Now i'm doing a transplant and pretty much have every thing to build the harness i just need to know if any one had any reference material on what guage each wire should be? i know this requires a fairly lengthy answer, but i could use the help?

Tough question but GM uses smaller gauge wire to save overall weight.
Consider most circuits are 10 amp so 16 gauge at the least and other circuits for 20 amp at least 14 gauge, something like main power feeds like Alt or starter I would suggest 12 gauge.

Why not just buy a wire loom out of a junk yard instead of hand building one ?

i guees i just like a challenge! thanks for the help.

any one else?