I thought that the Excursion used the same hitchs as an F250-F350, aren't they the same frame? A good hitch shop should beable to tell just by looking, if not park it nextto the same year pickup and take some measurements. Both Reese and Drawtite sell heavy duty hitchs that should fit, I have a Drawtite but if I had to do it over again I would get the Reese Titan-V rated at 12000/14000, it also has a 2 1/2" receiver but you can get adapters to use your old 2" draw bars for your lighter trailers.
Reese's on line catalog only goes up to 2000 but it does show 2 different width frames for the F250-350.
It's worth the money not to have something to worry about, a lot of people get away with the class3 hitches but they are an accident waiting to happen.