Blackwell has given up on Greenlight Arms for ANYTHING. They are using Dan Coonan receivers on their Yugo builds now and are trying to do their own soon. They are great to deal with, but Greenlight has screwed them like everybody else.
Call the number on their website is the best way to contact them, Eric usually always answers the phone.

Hi Mr. Krink, I really like that. I just got a build they did a Yugo underfolder an early or late type (without the trunnion bulges) built on an OOW receiver. I pick it up on Monday, it has been "parked" I got it from  NWEDDLE (great guy!) on the EE boards. These aren't cheap but it sure looks great! Eric at Blackwell Industries is really helpful too. He explained it all to me, over the phone. THANKS for the great pictures too! And by the way if an AK or anything doesn't have any gaps it hasn't been built right.  I am a Tool and Die maker, and that's just my $.02

They are doing an underfolder Yugo for me too, if they will ever get a rec!!!