I've done all my headgaskets in-frame. It depends on weather you consider pulling the engine to be a major PITA (which I do), versus just being uncomfortable. It's an 18 hour job without pulling the engine. I can only guess how much extra time that would add in my case, since I like to take my time, and would find other things that I would have to address in the process. I like the Ford/IH gaskets myself. They have been constantly improving them. The felpro are well respected, but I have no documented design changes on them. Whatever gaskets you use, make sure they have rubber around the water passages. The verdict is out on if it is helpfull around the oil passages or not. I've used both versions, and they both eventually leak, at least with factory head bolts.