If you used the wrong filter, meaning one hole in place of two, you would starve the rear pump supply. Actually, and I'm guessing here, all that means is the smaller sized rear pump would never take over, which is what it supposed to do at highway speed. I think the whole unit would continue proper lubrication, which is what's most important.... So, doubt you did any damage. As far as Dacron or the original brass screen filter, either will do fine, but you are going to want to find the right pieces parts for the extension and two hole filter type for your trans. A&A definately makes/sells the early type two hole extension you need for your pre '65 unit. Also, you didn't really say, are you having some sort of trouble, or is it working good as is??? HTH, Lefty71
***EDIT*** I do see you said weird shifting.... yes indeed, I think the valve body is confused once it starts looking for rear pump pressure, which is dead with your current set-up.....