Terry,
I can't help with the weather strip, but if you find out, let me know. Anyway, I have the same
oil pan on my 428. You have to sandwich one gasket between the windage tray and pan and one between the top of the tray and engine block. I also sealed mine with copper gasket sealer. Removel and cleaning of the pan is not a difficult job, but it is messy. Remember clean all surfaces very well and take your time. I suggest a good sealer because mine also leaked at first in the rear of the pan before I sealed it. I used FelPro gaskets for the Pan/Windage, I forget the #'s.
--Mike