1997 GMC Sierra 1500 electrical problems

HI, I have a 1997 gmc sierra 1500 with the 5.0l motor and it has about 350k miles on it.
The problem: The wipers come on while driving at random, and I have noticed that when they do the steering column energizes to 12v as well as the parking brake energizing to 12v. Not sure where to start looking for this short being that so many things are effected. It was so bad in fact that it shorted out my speed calibrator unit. Trying to avoid buying a new one of those 85$ things! Could it be in the firewall block? Or should I start with the column? Feeling lost, so any ideas would be great.
also all of the guages on the dash jump around when this happens as well.

Thanks in advance!
Todd