I have an 02 V-10 X. I originally had 3.73's. I knew I was swapping to 4.30's when I bought it. The 3.73's with a 9200lb TT will not be enjoyable. The 4.30's are what you want with a V-10.
Either of the 2 diesels will be good. If you can find a 6.0 that was "bulletproofed" early on it would be a good buy.
Keep in mind whatever X you buy you will have to do some suspension mods to help it tow well. I went with a Hellwig rear sway bar and air bags. Many people install F250/350 springs under the X, this fixes all the X's suspension shortcomings! Maybe go to Ford Truck Enthusiats and go to the Excursion forum and read all about the X's there. There are a lot of members that will give you plenty of advice!
Good luck!