Underhood wiring questions on the new truck...

[79 silverado]

So I brought home a new truck yesterday, and, in the underhood areas had a couple questions I was hoping to resolve without needing to see under the hood of my other truck which is currently 3 hrs away from where I am... I figure pictures are worth a thousand words, so I snapped some going from left to right under the hood that pertain to most of my questions...

General background, truck is a 1976, was originally 454 but now a 350, and is automatic. Originally A/C equipped, the compressor and lines have been removed.

First picture, there are (4) plus currently unattached off the harness from the a/c box. No wires are connected to the blower motor which is currently non-functional (obviously). Off memory from other vehicles, I think two of them belong on it? One of the small bolts that would attach the blower motor to the box is missing, and, I *think* originally it would have had a small metal tab off of it that served as a ground connection of some sort for a wire to plug onto? Likewise, the tab that comes out of the blower itself isn't hooked up. My take on things is the big plug, and its attached smaller plug would have been for the A/C compressor when it was there?

Second picture, there is a ground strap from the firewall that is unconnected, my assumption is it would have originally run perhaps to a manifold bolt? or back of engine block or something? Should this be reconnected, and if so where?

Un-pictured, the ground from the battery is currently attached to the forward most bolt on the passenger exh manifold. That doesn't sound familiar to me, but cast metal is cast metal... Is this as good of a site to ground it as any other, or, should I buy a longer cable and re-route it elsewhere?

Third picture, this empty plug in the center of the firewall I assume would be to attach a under-hood lamp, which there currently is not one on the truck (hood was replaced, lamp was not moved onto the new one) Is this correct?

Fourth picture, this is the block on the firewall towards the driverside with an assortment of grounds present. as you can see, two wires are snapped off or cut, and not longer grounding there. What remains is the following - one wire to the battery terminal; one into the main engine harness that from color appears to go to the distributor; one that runs into the harness that passes through the firewall at the a/c box. Are there other grounds that typically run here that I am missing, thus those two contacts that no longer have wires attached?

Fifth picture, an unknown wire that runs out of the firewall through the hole the speedometer cable enters from. it has a plus spliced onto it, and I didn't see anything under-hood it appears it should attach to... any ideas what it is for?

Also, the vacuum canister was removed, but runs strong and fine with out it, the vacuum ports on the q-jet are plugged as well. Should I seal the end of the steel line the rubber hose would normally have run to and forget about it? Or does it perform a venting function that needs to be there and should remain uncapped?

Those are just the initial questions I have, I'm sure there will be more. Right now I am focusing on getting the blower motor working, making sure wiring is 100%, then I will try to remedy the slow wipers which sometimes stop cranking....Then it's time to find what seem to be a slow weeping oil leak (passenger side of pan area it appears), followed by me moving to interior wiring, radio, ceiling light, etc... Thanks in advance guys...