CFD, I had the same issue with my Wix on my 5.9 Cummins, leaking at the seem. At the time I bought two. The other one was fine. I have heard of this problem before during last year on other forums. I still will buy Wix, but if it happens again, I will jump up and down with them. I like to think I'm buying the best with them. As a comment to the OP question, is it not the difference in his two filters is the length?
I realize that Fram filters have a bad reputation. I have always used the Fram 43 on my barracuda because of a header clearance issue. The 43 is a little bit shorter than the 16. I bought several of them several years ago, and my car is due an oil change now. I am looking for a replacement for the PH 43. I have always had good luck with the Fram brand, but I trust my FABO buddies when they say that Fram is not as good as it used to be.
I had to use the shorter filters on my van for clearance as you say because it would hit the frame. if not. On my 69' Dart, the adapter if set right, should give you room to fit a longer filter, along the exhaust. Note: The van also had headers.