TF = Task Force, the series truck you have, 55.2-59 .... yes "Amps" means ammeter - don't have a schematic for the change, but you can learn some about it
here, there's an article toward the bottom, although it discusses newer Dodge wiring, you might puzzle out the principles - and someone else here may have a simple diagram for GM trucks
there's no problem with the technology you have, it's been working fine for decades on thousands of vehicles, including yours and mine ... the main issue is age, so you might consider how good your present wiring is and how much previous folks have messed with it, not too hard to install a new repro harness, including a fuse panel for the goodies
Bill
