My next project is a Mann Accuracy Device. It's a HEAVY 21" stainless barrel on an '03A3 receiver, chambered in 7.62 NATO. They were used to test ammo batches and loads for accuracy. Others have done buildups that yield consistent sub .5MOA accuracy from a forward rest or bipod, and sub .3MOA from bench.
I'm planning on a tuned GI trigger (I like the feel of the two-stage setup), an S&K scope mount (03A3 receivers are HARD metal, drilling is problematic) and some variety of Mil-dot scope in the x18-x24 range. I still haven't decided on a stock yet, but it will be wood, not synthetic.
Oh, and all of my changes will be reversible, in case the "collector" market realizes how rare these things are.