Ignition Wire Question

Hey guys, I have a question here. I bought some Bosch ignition wires today (I know I know I should have bought motorcraft, but the Bosch were on for 60% off and my car needs a tune-up pretty bad.) Anyways, here is my question. I bought a set for a 6 cylinder Ford because those were the only ones they had on sale. (I paid $20 Canadian by the way, which is around $15 US) All the ends were the same as the 4 cylinder Ford set, and they are all the proper length, should there be any problems here? I am assuming that considering they should all work right because they fit and the wires themselves have the same structure as the 4 cylinder ones. The reason i ask you guys this is because the guy at the service section of the auto parts store I was at told me not to because they may not work. I just couldn't pass up the price, even if the don't work. Anyway, any help I would appreciate a lot. Thanks again.