GMC Repair: Chevy Silverado, chevy silverado, loose ground

Question
I have 93 Chevy silverado.  Right now the brake lights and wipers are not working when the ignition is on.  When the ignition is off the brake lights work.  Just recently we put a rebuilt engine in.  Checked fuses, for loose wires or grounds.  Radio, hazards, turn signals, a/c, guages, everything works except those two.  Everything worked perfect until we put the rebulit engine in.
 Please help me i will be very thankful

Answer
I don't have access to schematics for that truck right now, but I would say that you have a concern in the multi-function switch. That is going to be the only common point for both the wipers and the brake lights. Check for a loose ground back feeding through those circuits.