What function/purpose did they have? Are they positive 12 volt, or key only 12 volt, or? If so, yes, I would think you could use them as the new power source for your new LS harness/computer, if this is what your asking. If not, just run the power wires you need from your under-hood power center, where all your fuses are. Its really nice to get a hold of the wiring schematic for your 1989 truck. It will help you with every wire color & wire function question you have now AND into the future. Invaluable. And, contrary to popular belief, very easy to read & understand, lol. Any other questions?...fire away.