Building a FAL
It is very easy to build a FAL with one POSSIBLE exception.
Headspacing it.
If you put yours together and it headspaces then great.
If it doesn't you have two options: One is to locate the correct locking shoulder and install it on your rifle. Option 2 is to machine the barrel just like you were headspacing any other rifle.
So, you do need to buy or borrow a few specialized tools.
A few years ago, I bought an STG58 parts kit and a DSA receiver. I also bought a video from the American Gunsmithing Institute. That tape told me everything I needed to know about putting together a FAL. However, about that same time I ran into a guy at the SHOT show (at The High Road get together dinner at Battista's in Las Vegas) that is a gunsmith in Colorado. He told me that he put these kits together for $80. So, I figured I needed headspace guages at a minimum, what the heck ? So, I sent it to him. He put it together and sent it back the same day.
Now, the one million dollar question, who is he ?
I don't remember. I have his card around here some place.
He was a friend of Steve Smith.
This is the video. I was very happy with it and bought several others:
http://www.americangunsmith.com/view.php?id=38 You can even download some excerps from it and see what it is like.
http://www.americangunsmith.com/video.php?type=hi&vid=AGI122FAL_Clip_Hi.swf&id=38