I need to ask. Why are you trying to hook up wiring that is 36 years old?
All you need to run the engine is power to the starter, power to the hei, and power to the electric choke if equipped.
Here is a low cost system that just works on non computer controlled rides.
The 3 wire alternator runs to a junction block. The Off that junction block you run everything. You run the sensing and BAT wire off the alternator to the junction block. Off the junction block you run a wire to the starter and then to the battery.
The junction block is hot at all times. You run a main Hot wire off the junction block to the fuse panel. Note I said ONLY 1 Wire to the fuse panel. Only one wire running through the firewall to your inside fuse panel not 20+ potential bad connections. Off this fuse panel you run all the Hot at all times wires to the key, light switch, 4 ways, dome light, radio(memory) and whatever you want hot at all times. All of these items should have a fuse.
Off the key on position(also accessory) you run a wire back to the key on fuse block and now power the things you want on with the key into the on position. These include the electric choke, coil, radio, heater controls, heater, , power windows, alt gauge, and whatever electric things you want power to.
The key "start position terminal" wire runs to the starter relay with a inline fuse in between.
Use a common ground inside the cab with a through firewall connection that goes to the frame. Use a common ground on the engine that has a larger wire going to the frame. The negative battery terminal also goes to the frame.
Use terminals on a common bolt with any connections. Crimp the wires into the terminals make sure it is tight with a pull then place it on the bolt and tighten it down using a lock washer and bit of wire. You will never have loose connections unless they are at the cheap connection at the switch. Use a zip tie to cinch 4(or whatever the connection has) wires together to prevent this side from coming loose. This keeps the push in terminals from being pulled out of the inside of plastic switch.
Now you run relays AT your headlights, taillights, electric fans, horn, heater, defroster, and whatever high demand items you have. Having these relays AT the high power demand item reduces the wiring draw and leads to that item having full power at the item at all times.
I like to run one hot at all times wire and one key on hot wire to the rear of the car then bridge it before running it to a weather proof inline fuse before the relay itself.
You can run a single hot at all times wire and a single key on hot wire to the front of the car then bridge it running the other wiring to the high amp item.
This lets you run only 4 wires(2 front and 2 rear) to your 4 weather proof relay junction(bolts)(2 front and 2 rear). You then can run smaller wires off the junction bolts to the relays keeping things clean.
http://www.offroaders.com/info/tech-corner/reading/relay-diagram.gif
The link above is a good example of how to wire a relay to high demand items. You run the "yellow" 30 terminal to the junction block not the battery so that the alternator can supply full power to item as it needs power instead of needing to run that charge to the starter then battery cables before reaching the battery.
If you want to run a 2 terminal battery disconnect switch you simply place it between the junction block and starter wire. You can also use a 4 terminal disconnect switch that will kill power to junction block and coil to prevent the engine from running on in the event of a issue. Highly recommended as when in the off position power is only hot to the starter and wire leading up to the junction block before the switch interrupts that flow. You never need to worry about a embarrassing moment from a dead battery from something draining it again. You can run a single wire(with inline fuse) off the stud on the starter to the radio memory wire which keeps all your stations. I can not think of any other thing that you would want to bypass the battery disconnect switch.
Now the above system is very basic and low cost.
I am talking about a main bolt passing through the firewall as a main ground, a main bolt as a frame ground. (seriously bolts and nuts to hold them in place then bolts with lock washers to hold your terminals in place no need to protect them from grounding our of course) $10
Junction block$10
Catalog
A universal hot at all times fuse panel, a universal key on hot fuse panel These should be separate panels if possible as it simpflies things. Two panels like this will give you more then enough fuses to wire up your truck.
Universal Car Boat 10 Way Fuses Box Circuit Standard Ato Blade Fuse Holder | eBay
Note these have bolt/screw in connections not blade connections that you can pull out or can work loose. The fuses are blade style but that is the standard and is easy to find/replace.
For $100 you can get a set of good fuse panels.
Universal Car Boat 10 Way Fuses Box Circuit Standard Ato Blade Fuse Holder | eBay
For another $200(going high, you can do better) you can get all the wiring you need to run your truck. Including 0 gauge wire from the battery to the starter to the junction block. 4 Gauge off the alternator to the junction block, 4 gauge for your Main grounds, your high amp inline fuse for the starter solenoid, all your relays/flashers(buy them in bulk on eBay), round connections, and some heat shrink.
Now you can reuse your switches and wiring leading to them. They either work or they do not and replacing the old OEM stuff with some cheap replacement is not recommended. If you want to have the entire system all new you can replace these switches with ones from respectable suppliers for under $150.
You are going to loose that bulky firewall connection that you have been playing with, most of the grounds that hang over the fenders, your firewall will become much cleaner, and you can easily hide most of the wiring making the engine the focus of the engine bay as it should be.
So your talking around $350ish (not including new switches) and the truck will have a majority of the wiring replaced. Not only with it be newer it will be better organized, perform better, and will have better more reliable connections.
Here is some other ways to do what I have described.
Fuse Panel, Ignition Switches, Etc... How to Wire Stuff Up Under the Dash.
http://www.madelectrical.com/electrical-tech.shtml