I'd like an AR-47 too, but these guys have a point. Spend the extra $+time buying dedicated 7.62x39 AR mags, like C-mags. You'll be saving yourself frustration, labor, and possibly a bolt carrier and/or lower reciever.
It's kind of like modifying an SKS to take AK mags; you'd have to remove metal at critically beefy points. We must assume those points are beefed-up for a reason and it is better not to make irreversable changes.