67 chevy 250. No crank, start, lights

[Mgicm]

So I have a 67 chevy step van which is same as c10 basically. Started it fine today. Wenr back about an hour later and nothing. No crank, no dash lights ,no headlights, no nothing. Brand new battery today and same. 12v light test showed power at big bolt on starter. Nothing on other terminal which has wire to ignition switch. Fuses all look good. This one has me stumped as it just started an hour ago. I am stumped. I put screwdriver across both starter bolts..big spark and sounded like it was cranking. Screwdriver fell as it startled me a bit..assumed I would get nothing. Just don't get it...why no power anywhere...and it worked.fine earlier.

A side bizarre thing is I found something dangling under the truck..with wires to it. No idea what it is.. pic attched. Looks like some kind of switch.

Thanks kevin