Tooling isn't a problem... (hehe)
Probably the only things I'd need to get is a clamping block set, and possibly a tap.
http://www.cncguns.com/tooling.html (tool/tips/resources)
The only reason I mention DPMS is because they are the only people I am aware of that make a 7.62x39 ar-15 barrel.
If I knew of someone who had an ar-15 lower that they wanted to unload, I wouldn't mind going that route. (If it was in serviceable condition.)
Really the issue is the upper and all the internals.
I’ve seen those; despite the claims, most of the time people get the buffer tube area wrong and ruin the piece. To each their own, though.
Why would you want an AR in 7.62x39 anyway???