grab anything and everything you can. I got the whole truck for my swap and I swipped everything! every single wiring in that thing along with clutch slave, master, lines, fuel lines etc. just in case. never know what you will need once your in there.
I like my 85 dash and going to keep it. you should be able to sit down with a factory wiring book and sort your wires out to the ones you need. get rid of the excess stuff and clean up the harness. its time consuming to do right but IMO making it look like it belongs is just as important as having it work correctly.