as we have discussed at length in other threads (pun intended), cold headed and rolled threads are superior to cut threads and heads, considerably so in fatigue. aside from that, he's got 1000 of these to do.Can you drill half way, flip it, and drill the other side?
I'd much rather make a bolt from scratch than modify cold-headed hardware.
a high quality fastener should be consistently in a fairly narrow range of hardness. a cheap fastener can be all over the place.
Holo-Krome or ARP....