crank pulley????????????????????

Hi--Hope this is just a simple question, but it's got me stumped. I went to put the crank pulley on my 340. Had several harmonic balancers, this was the best. I can only get four bolts in the pulley-the other two don't line up. I assumed all pulleys were the same. Every pulley I have is exactly the same. Did they make two different pulley bolt patterns? Early, late, don't know. Thanks and Happy Holidays!!!