340 heads??

Ma Mopar didn't make it real easy to identify heads since they used the same casting number on several of them. I have seen several mix and match cast numbers/letters i.e. 915 castings with J,O,U and 587 with no letter, J, O, and U I just look them over and see what they really are. Books are almost useless sometimes since they made so many variances in them. The one thing that is for sure is except for the TA/AAR head all the others are really closely made and flow nearly the same. Like someone said above they have to have the offset pushrods to be AAR/TA heads. I've also read X heads are better flowing. I had my 68 340 X heads flowed before I ported them and they were no better than the numbers I've seen for any 2.02/1.60 valve J head.