It was at this point that I started reinstalling the FCG (fire control group), and then I realized -- I was missing some parts. Brian at DinzagArms had forgotten to toss in one little bag of e-clips, and I was stuck. He apologized profusely and promised to send some out immediately. Since I couldn't get any further with the FCG, I decided to skip ahead and install the bullet guide. Stock Saiga magazines have a taller front lip that guides the round into the chamber, and using regular milsurp AK mags won't work unless you install a guide to fill the gap.
Brian at DinzagArms offers a bullet guide kit that includes a drill bit, a tap, the bullet guide and screw. I was extremely nervous about this process, as the "Woops!" factor is fairly high here, but I made a nice deep divot in the center of the trunnion, drilled a good straight hole, and then went REALLY, REALLY SLOW with the tap. I also dripped a few drops of oil into the hole as I was tapping it, and when I would feel it start to bind I'd back it off a half turn to break up the chips.
Here's the bullet guide, nicely centered.
Rather than wait on the e-clips to arrive in the mail, I headed to Lowe's and test-fit some e-clips until I found the right size. This allowed me to forge ahead with the FCG, and after a LOT of fiddling, everything was back in in place. I will mention that a lot of guys abandon the bolt-hold-open lever at this point, but I decided I wanted to retain it so I carefully ground down the lever to an inconspicuous size, and then reinstalled it.
Once the FCG was finished, I was able to install the new KVAR NATO-length buttstock. I also received the forearm I was waiting on, so that went on too. It's a Surefire (not to be confused with the flashlight company) railed grip that fits directly on the Saiga without any handguard retainer. It's extremely solid and I'm very pleased with it.
The finished product, with the stock Saiga mag.
And a "just for show" pic with a 30 round Promag.
As soon as I get some milsurp AK mags, I'll carefully file down the magazine release to fit those. I have no intention on using the Promags, so I figured I wouldn't mess with the magazine release until necessary.
This was a moderately challenging process, but it was great fun and I learned a lot about the inner workings of my Saiga (there aren't a lot of inner workings, but what there are, I learned). I'm much happier with the length, balance, and feel of the rifle now, and I'm very pleased to be able to legally use any milsurp AK mag now.
The most helpful resources for this project were:
http://www.cross-conn.com/Saiga_Conversion/
http://www.youtube.com/user/rjs3484
http://forum.saiga-12.com/index.php?
http://www.dinzagarms.com/index.html
If you are thinking about buying a Saiga, or converting one you already own, I highly recommend it.