Sorta rambling post incoming.
Backstory: I've gotten to the point with my truck that I'm starting to look at power mods. I've re-geared it for the bigger tires, and I've taken care of most of the deferred maintenance. I've got 154k on the truck, it has the 4r70w transmission, and 4wd. The internet tells me that's too many miles to bother with and my transmission will explode if I add any horsepower. I'm hoping that's not true.
Goals: Some more power and staying smog legal. Right now I'm mostly looking at the exhaust, primarily for that sweet V8 rumble, and because I've heard Ford choked these trucks a bit. Is it work replacing the y-pipe and the other bits downstream and keeping the factory exhaust manifolds? I have full intentions of keeping the catalytic converter. I have a cracked manifold right now, so it's a good time to replace them both with shortys if it's worth it. Otherwise I'm thinking a single 3" pipe running from the y-pipe, through a nice sounding muffler, and then to a more protected exit. Maybe a turndown in front of the diff? The factory location behind the passenger side tire is far too low for off-road fun. Same with anything exiting under the bumper. I don't want anything I'll have to yell over on the freeway.