M1 Air-Gap Intake Manifold for a 340 motor

I know this topic weaves through a lot of forums, but I've spent hours looking for a definitive answer and had no luck. I have a 1970 Duster with a 340 and have been looking for an M1 Single Plane Air-Gap intake manifold to put on it. The problem is that I don't know the proper part number/casting number for my application. I have LA heads that are stamped with the letter "O" and I have seen at least three (3) similar casting numbers that are very similar but I don't know their differences. The numbers are P4452891 (I think this is the one I need), P4452893 (I see this one a lot), and P4452898. I've also seen a P4876334 but I think that is for W5 heads. Can anyone help me understand the difference and let me know which one is right for my car? I know they aren't made anymore and are hard to find but I have found a few of the P4452893's out there, just not sure they'll fit on my set up. Thanks in advance for your help.