Thinking of buying a 2012 Keystone Cougar XLite 31SQB

I just did a quick search and found the Ford 2002 towing guide which says that with a 3.73 rear end that he can pull a trailer with a max loaded weight of 10,100 with a 4X2 and 9600 with the 4X4. If he has a 4.10 rear end, then it goes up to 10,500 with the 4X2 and 11,000 with the 4X4 (this does seem a bit strange that the 4X4 is higher for the 4.10 rear end, but that is what it says).
check here https://www.fleet.ford.com/resources/ford/general/pdf/towingguides/2002_All.pdf