I work in an electrical mfg facility and design harnesses all day long so I know how much information is needed. If you have harnesses to reference (length, gauge, type, connecotors, etc...) its doable to a degree.
I thought about doing this myself last year, however, after looking at all the required harnesses it became painfully obvious to me that it just wouldnt be worth it to me. Aside from the time to remove and tag all the existing harnesses/building new ones, I would have a real hard time finding all the right connectors and gromets for the car. If I were to re-use the existing ones it would just further complicate things. Getting the wires out of connectors isnt that hard with the right tool (usually special tools that are hard to find), but 38 year old connector pins are a whole other story. Not to mention that re-using old electrical componenets is never a good idea.
Now, keep in mind that unless you follow the factory color coding you will not have a schematic that reflects your wiring anymore. So you would need to do that or design your own schematic.
My wiring wasnt that bad and didnt need to be replaced as I originally thought (just had to de-bug it) so I didnt worry about it anymore.

I guess it depends on what your looking to do?
Do you have existing wiring in the car now for reference or is this a bare car and you need to re-wire the whole thing from scratch?
If you have a reference I would say you can do some yourself but if you dont its going to be tough.
I would agree with old_fart on the dash harness. Aside from fire, its just a pain and very complex harness. It would be a task to make this one on your own. The others I think are doable.
Elaborate on your game plan a little more for me, I may be able to help you out a bit. I have acess to a lot of neat tools here.
I can also have someone here build you a harness off the clock if we can give them a design reference.