1993 Chevy Silverado Variable charge, no dash lights and ru

Electrical problem
1993 Chevy Silverado V8 Two Wheel Drive Manual 245k miles

My voltage charge varies, sometimes normal sometimes drops to the red zone.

Before, when my voltage drops the dash lights would dim and the gauges would drop or stop working and my speedometer needle would jump back and forth and my head lights would dim.

I have done the basics:
*New battery (it tested fine, but it was seven years on a five year battery).
*New alternator (tested fine, but I had 215k miles on it so I replaced it)
*Checked the fuses in the fuse box (all are fine).

Now, voltage is still low and drops to the red zone, my dash lights do not work most of time and my running lights to not work most of time, when my dash lights do work so do my running lights. My speedometer needle still jumps around.

I figure my dash is bad or there is a capacitor somewhere that needs replacement. Any suggestions other than to get a new truck.

Thanks
Jim