i just bought a spikes tactical 5.45x39 complete upper, two cases of surplus ammo and a bunch of mags. still waiting on lpk from palmetto( should arrive this week).
From my research it looks like you better off using dedicated 5.45 ar mags, verses modifying standard 5.56 mags.
ASC and C-Products makes 5.45 ar mags
If you want some mags, let me know i can spare some