I'd probably just check them against each other, or another bolt if you have one (I think they are M10x1.5 thread pitch) to make sure the threads haven't stretched. Then put them all upright in a line and see if they are about the same length, if I couldn't see any differences I would re-use them

OR, I could scrounge up the set of E headbolts I have laying around (brand new) and sell em' to you pretty cheap. I lost the receipt and cant take them back

Oh, one question, could you describe the E headbolts to me? I want to make sure thats what they accidentally gave me. They have kinda a shoulder, or built in washer of sorts under the actual hex head right?