Hope this helps?
I don't know if i can shed any light but i bought the exact tail light off of e-bay almost three years ago and it still works...well...some of it,anyway?
Mine had the white LEDs across the bottom for the plate light up but after about a year,it went out.The tail light still goes strong though.I hate that i just caught this thread because i JUST threw the instructions away when cleaning out my closet!!! I am going to do my own custom tail light and am gonna do away with the assy i have now.I CAN tell you that the 2 white boxes are for the turn signals to keep them from blinking fast.However;Be careful as to what kind of front signals you use because when i took my stock ones off,they started doing the fast blink dance.Hope this helps a lil??? Good luck and once you get it going,you'll like it!