Hmm...I'm still not sure if I understand you. Regardless, I would run new grounds on sheer principle. In the car stereo world, we do an upgrade called "the big 3". To do this, you replace three primary cables in the electrical system.
1) The main charging cable from the alternator to the battery.
2) The main ground cable from the battery to the chassis.
3) The main ground cable from the block to the chassis.
This ensures a good grounding and charging circuit from alternator to battery to chassis. I usually use at least 8 AWG wire, and sometimes go up to 4 AWG or even 1/0 depending on the demands from the vehicle.
I know a lot of this might not be relavent to your situation, but 1) its good practice to make sure the vehicle is properly grounded, and 2) its just good information to log away in the memory banks.
Hope it helps.