Strange Problem Help Please

I have a 1995 Chevy 1500 5.0 automatic. I have recently had the heads rebuilt, they were installed by a certified mechanic. Shortly after that is when the problems began.
The shift indicator lights comes on and off, when it is on everything is fine, when it goes off the abs and brake warning lights flash, the engine stumbles for a few seconds, the AC and heater quits working, the windshield wipers and squirter quits working, and the brake lights work in reverese including the emergency flashers. I have replaced all the relays and pulled apart the harness from beginning to end trying to find a short, I have pulled apart the dash and stering column and have found no shorts. I treid pulling fuses one by one to find it also but to no avail. When the ignition is in the acc position pressing the brake pedal will make the shift indicator light turn off and on like a switch. The problem has gotten worse, it used to happen every once in a while now I have a hard time getting the shift idicator light to come on, I have to change gears back and forth to get it to come on and it usually will go out within 5 mins. Any help will be most appriciated!!

look back at everything that would need to be moved to replace the heads. chances are when they replaced the heads a wire got caught or got damaged. when weird things happen its usually short from wire to wire.

While your at it make sure the ground wire on the passenger side head is connected and tight. Also look at the wiring that goes down to the starter from the back of the motor could be its found its way to the exhaust manifold and burnt enough to short. please post findings.

Thanks guys, I have checked all the grounds everywhere and have been all through the harness once looking for any obvious shorts, I still have the harness pulled completely apart so I'm going to go through it again with a fine toothed comb, I agree with the logic of a wire shorting out somewhere, I just haven't found one yet. I hate electrical problems.