You stated you have a custom wire loom. does it have a Maxi Fuse or fusable link?? You will lose power if it popped and/or melted. of course you will have to determine why it popped before replacing it.
Incase you are not sure what I am referring to, this is the Maxi-Fuse on my '55. 50 Amps. All power goes thru it first, then to fuse block.