Immaculate condition with 176K on the 5.0

Bumper hitch appears to be stock for tow package.
My wife and I recently bought a used 1993 Ford E150 Eclipse Custom Conversion Van and want to use it to tow a 1976 Coachman Cadet 21' Travel Trailer weighing approximately 4300 pounds. My questions are simply how do I know if the tow package on my van is original equipment or aftermarket, it is not a towbar unit in the back but a bumper mount. The tires show to be 215 75R 15 stock but it has 235 75R 15 LT tires so my concern is whether the tires will affect towing capability and how do I identify if my tow package is stock. Thank You.