Correct me if im wrong, but im pretty sure johns from Temple performance's kit is just a tool to straighten out what most people call the "lasagna" of the gasket which is when the gasket itself geta way appearance to it, to correct the issue you need to find a donor window with a good gasket if yours is deteriorated or damaged, the lasagna can be fixed, yes, but if it is any more severe id suggest searching ebay for a replacement, the actualy gasket on a marks rear window is physically made attached as one piece with the back glass if that makes sense, so its a little mroe difficult than re-glazing it with a new seal, for a CORRECT fix i would find a used replacement with a nice gasket for 250-400$ and swap it in, or u can always order a new one from ford but they are about 900$