I went looking around for pictures on how to take apart a fuse block (box?) and came up with a bunch of information on how to do it... but we all love pictures so I wasn't satisfied with what I was coming up with.
Fuse block front:
Fuse block bare chassis:
Back of fuse block:
Back of bulkhead connection showing the elusive 8mm head (however apparently sometimes 7mm, 6mm, or 1/4") bolt:
Here's the extraction tool I made using a piece of stainless TIG filler. It's roughly 1/4" from tip to tip and I tapered the ends so it would fit nicely around the female fuse termina