How to reassemble spring assembly on Shimano M520 SPD pedals
I figured out how to reassemble this after some examination of the assembly diagram.

I took the body cover off (see item labeled #4 in diagram). 
Then I reassembled the spring / tensioner assembly without tension on the springs. I used a magnet to hold the bolt in place while I did this.
 Then I attempted to put the body cover back on.  I couldn't exactly squeeze it on due to the tensioned back section.  So, I put it on loosly with a few threads of the three bolts screwed in. It was loose enough to hang on there, but it was at a slightly awkward angle due to pressure from the tensioned back section. 
I then was able to slowly tighten the bolts and force back the tensioned back section with a screwdriver until I could snap the body cover in place.
The bolts held the body plate down and prevented it from moving due to pressure from the tensioned back section. and I completed tightening all the bolts and now have a functioning pedal.