Which rig?
If it's on the 1990, it's a current limiter for the fuel pump, and it was installed to cut noise slightly (there were complaints due to fuel pump "hum" being carried through the frame rails, and audible by the driver.) That ballast resistor may be safely eliminated entirely, if you choose. My 87 never had one, and I pulled the one out of my 88 years ago.
If it's on the 85, see if it is inline to the ignition coil - if it is, you have to keep it. It helps prevent premature coil burnout - it would be bypassed while cranking, then brought into circuit when the engine is running normally.
As I recall, nichrome wire is usually used for ballast resistors, since it has a controllable resistance by length and section, and that figure is higher than copper (which makes it better for low-resistance elements.)
These resistors aren't usually well-made in a structural sense - I've usually been surprised when I'd get one that had two tight terminals. As long as the "core rod" is sound (the one holding the shape of the resistance wire) and the resistance element moves when you move a terminal, it's nothing to worry about.
It is possible to solder dissimilar metals, but it's usually easier to crimp them. It takes a little patience and practise to solder copper to something else - but you can usually braze dissimilar metals with practise, and soldering is a related process (joining is accomplished by addition of filler metal, and not by actual fusion.)
5-90
