Shift Selector Assembly/Rail Pics
http://para.noid.org/~lj/T56/T56.htm
If I hadn't sealed mine up last night, I coulda snapped some as well.
Assuming you've got the trans flat on its face, with the top of the tranny being the 'center' for left/right reference... I line up the 1-2 and 3-4 flat pieces to the left of the round selector dowel, and then I swing the 5-6 and R flat pieces to the right of the round selector dowel. I then put the case on, and use a flashlight and line up the rail bolts. Most of the time I have to slightly lift the 5-6 / R shift rail assembly to get the rail bolt slots to line up.
Here's another view of how it's kinda put together (but with only 1 black piece, as I couldn't find the other one - I have a junk parts trans out in my shop).
This is probably the worst part of the trans.
The first time I did it, it took me about a half dozen times before I got it right. But after you understand how the little dowel selects each of the gears (push one direction, it selects that fork... push the other, it goes in the other gear... slide it laterally across the forks, it's in neutral). 

