1995 Dodge Dakota Tach all over, lights dimming, what is go

Electrical problem
1995 Dodge Dakota 6 cyl Two Wheel Drive Automatic

Does the pickup coil in the distributor or the crank sensor determine the engine speed displayed on the tachometer?

This vehicle is another one of those weird electrical freakazoids.

Vehicle brought in because it would quit running all of a sudden. Determined there was a fuel pump issue. Replaced fuel pump and ignition coil, and it runs. Took it for a test drive last night, and all of a sudden, the lights would dim, the tach and speedometer were all over the place but the engine wasn't changing speed it didn't seem, then it would try to die out. When it died, I'd turn it on 3 times to clear the computer, and then it'd start again. But not much further, lights would go dim, it'd start to buck, tack and speedo all over the place, but the engine wasn't revving up. Gimme some direction guys! :)