New engine electrical problems.

[Jakes-66-K10]

I've installed a new GM crate engine into my '70 Chev. I'm running into all kinds of problems, can someone answer a few of these questions?

One would be I have a weird wire attached to a light that is coming out of my steering column. Not even sure where that's supposed to go, or what it is.

Would someone mind giving me a breakdown on which of these wires go where. My wiring diagram shows the yellow and purple go to the starter, but perhaps the yellow is not needed anymore since I have an HEI?

And I know the greenwire in this pic is for my water temp, but what's the yellow wire supposed to be for? Both yellow wires seem to be coming out of the same wire into the fuse box. I am not completely ignorant to electrical things, but I could sure use some help on what wires are supposed to go where (treat me like a newb!). I'm really confused because it's a newer engine and some of these wires may not be needed. But I don't know...

Anyone up for this challenge to help get another truck on the road? I'm not getting any power anywhere, so could use a quick walkthrough wiring up a new engine.