Colbymac, welcome!
Might wish to have Mods separate your post into a new thread which would make more sense than piggybacking onto someone elses..
I will say, you should have the 3valve 5.4 which should have at least 300 HP which from my own experiences with a 97, then 2003, and 2006 F250s which are about 1,000 lbs heavier than F150s of the same yrs you should have very little issues with 5400 lbs worth of trailer. I towed 26ft TT when loaded was 6500 lbs and the 06 300HP 5.4 handled that very well.
You won't win any hole shot races at the stop lights but it will pull nicely.
100K miles on those engines is not a problem, had our 03 5.4 go 240K miles before I sold that one and the engine still was running strong. The 3V versions, you do have the possibility of the cam phasers going bad and/or the timing chain tensioners having issues, make sure you change your oil on severe usage schedule when towing to make sure you have fresh oil all the time which helps the tensioners and the cam phasers (they use the engine oil pressure to activate them).