67 GMC super custom build

[chewychevy67]

So I've installed the new block and added the few small extras to my main harness I wanted and I removed the original 12 gauge wire from it and remade it on 10 gauge. Probably wasnt required to do it but I wanted to do it. Less worry about heat and resistance. Now I have a question. My original 67 ac harness has a in line fuse just as it starts out from the main harness before the switch. I've never seen this before. Is it a 67 only thing? Anyone know what size fuse was in here originally?