Looking around under the hood and noticed a homeless wire. I found where it came from. There's a thing that looks like a condenser as in points and condenser (showing my age here) off to the side of the coil pack. It's circled in blue in the picture. What is this thing called and what does it do? Truck runs fine without it but I'd like to get a new one.

It looks like a condenser used for noise suppression (static and/or whine) that you might hear on AM radio.  Volvo used them on their ignition coil, attached to the negative terminal, and on the alternators. 

I'll bet that's it. Only 1 black wire going to it. The radio plays good with no noise since I found and fixed a rubbed through speaker wire. I might just forget about it.