Been searching and found the exhaust tip is 3” diameter. My stock one isn’t even a tip, it’s just a metal pipe? So would a new tip just slide over the exisiting pipe or do I have to do something else to install a new tip? Not sure how far over a new one will go over the pipe.

tia

2015 XLT Non—EB v6

 

Go outside with a tape measure to measure the O.D.
Take that tape measure with you to the auto parts store and purchase the tip you prefer most, as long as the I.D. will clamp over the pipe's O.D. of your truck.
Alternatively, drop by a muffler shop in your town and tell them you'd like just the tip.
They will show you their tips, you'll pick your favorite and they will weld it on for you.

A shop will cut off the excess pipe, well on the new, so the fit/finish looks nice. You should do the same, afte rpurchaseing the tip you like, hold it up next to the tailpipe on your truck, mark it then cut it with a hacksaw. The new tip you find should have a band clamp. You will need a little bit to insert into the tip to bite on so don't cut off too much.
The physical tip diameter as visible from the outside will be larger than 3", if your factory pipe is 3" now. They are sort of like a megaphone. I can't remember the pipe diameter of my 5.4 motor, but I had a cat back system installed. They bent and installed (welded) new pipe and muffler as well as a 4" megaphone tip.