2WD and 4WD matters as well
Page 9 here for 2000:
https://www.fleet.ford.com/truckbbas/non-html/2000/bbcamper.pdf
Above would apply for the 1999 as well
GCRW-Gross Combination Weight Rating is a weight to watch out for, say truck weights 3,500lbs and driver/passenger weigh 300lbs, then say you put 500lbs of gear in the bed:
3,500+300+500= 4,300lbs
Say your truck's GCRW is 6,000lbs, then minus 4,300lbs = 1,700lbs
So max trailer weight on this trip would be 1,700lbs, NOT max trailer weight listed above
If GCRW was 7,500lbs then minus 4,300lbs = 3,200lbs, NOT max trailer weight listed above.
And just as a heads up, if you think trailer weight will be over 50% of vehicle weight then use trailer brakes, it is required in some places, but generally a good idea in all places