Truck just quit running

[1969SurvivorC20CST]

OK guys I've started a different thread on this 69 C20 396 survivor truck. After I installed the factory exhaust system today the truck was running on my lift when suddenly it just died. Just as if you had turned off the key switch. I was baffled for a minute or two. Pulled the coil wire at distributor and had someone crank it. Cranked fast but no fire. Hmm. Checked for 12v at the coil positive with key on, nothing. So I'm standing in front of truck thinking and I turn towards the battery and the plastic junction block with the fuse holder. I had been curious about it and it's function since first working on the truck. So just for chits & giggles I pulled it apart and what was left of a glass fuse fell out. Hmmmm I thought, could this somehow be connected to the truck dying. So I cleaned it out good and jumped both ends with test lead. Fired right up. So can anyone tell me what part this terminal block plays in the starting, running of the truck and what size fuse is supposed to be there??