I ran plumbers tape from the factory bracket on the right side of the opening, across the bottom of the sterieo, then over the top of the steering column to the bolt on the left side. I also added an L shaped ridged bracket to the dash bottom to keep it from sliding back.
I'm currently replacing my receiver also and am contimplating installing the heavy old 8-track player that came in the car. It's from the 70's (not original) but the sound is a little weak. What do think of the that Pioneer unit you purchased?