Odd Electrical Problem

Ok this is an odd one. I have a 1988 Bronco II (Edie Bower Edition) I get into the truck and start it up, the "rear anitlock" light come on and the power windows/locks and radio don't work. I then put the truck into drive and go. After a bit the "rear anitlock" light turns off and the rest of the electical works fine. Now at this point when I hit a bump in the road (doesn't have to be a big one) the electrical power to the engine shuts off just for a second (RPM's drop to zero) then the power is restored and everything runs well. So now I am driving down the road bumping along with the engine cutting on and off. When I get to a destination and put the truck into park (or anyother gear) it cuts off. I then start it back up, put it in reverse or anyother gear and it cuts off. I have to start the truck in gear, (the neutral safety switch must be bypassed). Any ideas of where to possibley look for a short or bad sencor or anything. Thanks for any help that anyone can come up with.

Have you checked the ground connections? (chassi-connection)
By the sound of it, it should be ground failure somewhere...
I really don´t know where to start looking. But all ground conn. under the hood is worth checking...
Maybe someone knows in this forum...