Can anyone point me in the right direction or post what the FORD FACTORY towing (fifth wheel) is for the 6.4 and 6.0 engines? F350 club 4x4.

I am looking at getting back into a Ford but am looking to tow a heavy 5th wheel and I have explored the new truck ratings but am having a hard time finding the older (used) ones for any of the manufacturers, just alot of mine will tow ... I want to be within factory specs because I will be towing all over the country and through Canada to Alaska.

Thanks