I was looking at Dododex and they have base stats of the different animals when you first pull them up. I’m sure there’s some variance because not all wilds are the same but it looks like the wooly rhino is gonna have the most starting weight capacity in general.
Dire Bear: 650
Ravager: 500 (they have a lot of weight reduction perks but not enough for what I need it for)
Wooly Rhino: 750