My best guess is that the 8 "rubber spacers" are for the rear shackles. The rest is for the front and the two square parts you didn't mention are cushions that go between the front cab mount and the frame.
Sorry I can't be more help with the rear shackles, I haven't gotten to that part yet other than a casual assessment of their condition, but I do believe they just bolt directly... I know they do to the floor, I'm just not positive about the frame.
