If properly converted, I don't see it affecting the towing capacity any more than the additional weight adds. Actually will be more stable with the super long wheelbase.
But as said above, will take a football field to make a u turn.
Sucks there's no options for heavy towing and more than 5-6 passengers. RIP, Excursion.....
Still think, the first mfg to re introduce a HD diesel suv will have a good market for a while. The old ones are all dying. Neighbor just paid over $20k for a 13 year old V10 excursion with 85kmi. Only option for him to tow his TT and haul 5 kids.