Is this only for 7.62x39? Or can 7.62x51 play too?
I found AKM receivers at The Gun Exchange in San Jose. They have several types of AK receivers to choose from, IIRC they were about $150.00 each.
The Gun Exchange also has MGI multi caliber lowers on order. The MGI lower uses caliber specific detachable mag wells to allow caliber changes. Kinda' pricey at $469.00+ but it is an option.
They also have Hesse/Vulcan pinned .308 lowers on order. Call for pricing and further info. When I went in there a week ago they still didn't have any in stock and were unsure as to the price. Nice guys, very willing to help. (408) 265-4867.
Sonoma Fire arms in Sacramento has stripped Hesse/Vulcan .308 lowers for $349.00. If you have been to a gun show in the bay area or the central valley you have seen these folks. They have a selection of M1A's too. Very nice people who are not hesitant to sell legal rifles to the public. (916)761-0209.
The Hesse/Vulcan lowers have had mixed reviews so far, but the problems seem to be with magazine fit of the pinned mags.