Help me figure out how my '69 C10 was lowered

[blf]

Hey folks --

Second post on the board, and I'm here looking for help. There will probably be a lot of that coming from me so I thank you in advance!

I'm posted a few pictures from underneath my truck -- it's been lowered, and I'm not sure how. I haven't been around stock trucks enough to know what to look for. I'm interested in knowing just of of curiosity, but also because I may want to go back to stock height some day.

So -- what do I have here? What's been changed to lower this truck? Let me know if I need to take different/better pictures, take a wheel off, etc.

Here's a link to the album with photos.