Who'd you get the lower and parts kit from? I'm very interested in doing this, as well. There's just so much out there to choose from.
ak-builder.com
The ‘lower’ is actually called a ‘receiver flat’ that is bent using a hydraulic press you can buy for cheap at Harbor Freight. I am using a 6-ton.
There are lots of resources online that teach you to build your own and heat treat your own receiver (which is only done to the hammer and trigger pin holes).