Dies can come from RCBS, Redding, Hornady and CH. .338 brass, yes. Either .338 necked up or .458 necked down. Would fit fine in standard large ring 8mm/30-06 length action. Would actually better a .358 Norma some due to better expansion ratio and .375 bullets designed for larger game. Most .35 bullets are designed for .358 Win/.35 Whelen speeds. At reasonable ranges with a good shooter few critters would ever notice that it wasn't a true H&H.