Thanks for the suggestions. I soaked it 50/50 water vinegar and holy crap did that ever do the trick. I will post some pictures of it clean tomorrow.
As for the modern fuse box, I thought about it but this one has worked fine for 30 years and it's a lot less work than mocking up a new one. Now if I can just find my intermittent ground fault on the starter wiring I'll be happy
