No power after engine install HELP

[JFC10]

Hi all

I recently finished slamming the 350 back into my '69 C10. It came out to install a timing chain, drop the oil pan, a new intake, to check for catastrophic damage and misc. other stuff. Only took me 3 nights, gotta be a personal best

So I get everything bolted up, I'm in a rush and I hook up all the wiring and small stuff. I had it all hooked up, neglecting the alternator leads.
Well, sat the starter in the engine bay (grounded) and hooked it up to make sure I had it right before crawling under there again.
Starter wires (with the starter hooked up) suck...

Well I go to bump the key to make sure it spins, and there's a click, and I see the needles on the gauges jump a little and go back down. Nothing electric works now...

So my question: what will burn/pop if all the alternator leads were touching ground when I turned the key?

I have the big hot lead going to the starter (know I got that right) and one small yellow, and bigger purple lead that are bolted to posts on opposite sides of the starter solenoid. I have an S and an R marked on those two posts.
Going to be honest: totally guessed on which of these small leads went where on the solenoid, based on how the wires were bent into shape.

Now I have all the leads correctly hooked up on the alternator, and no cab lights, headlights, no crank, no gauges, absolutely nothing. ALL the fuses are fine, I checked them about 10 times. Humor me and let's just say they are all good...
Assuming all the wiring is stock (the farmer who owned this before me made some questionable fixes, based on the yarn he used to affix wiring harnesses) what could have happened? Fusible link?? Everything I can see looks fine, no burns or stretchy wires

Any advice would be greatly appreciated
Thanks