My pivots were already at the origin. That isnt the problem. I had no choice but to go ahead and combine all of the objects then mirror them.

Here is the finished back. I will now need to do windows, lights and bevel up the body. Btw, does anyone know if I draw my own reference images and have them same size (front, back, height of front and side, etc) and just draw by hand, will I be able to to create a model with it?