The deciding factor on towing would be the rear axle setup. The stock KJ CRD is rated at 5000 lbs in the US. I think the international version is rated higher, but there are no differences in the rear axle setup.
Lets look at each component
Most of the SFA conversions have either kept the 8.25 or gone with a stronger rear axle - this is not a limiter
Most of the SFA conversions have replaced the 3 link wishbone with a 4 link setup. The stock center link was a single point of failure, and the 4 link should be stronger and more stable assuming geometry is correct and the welding of the link ends is quality
The wishbone is a beefy chunk of metal. Depending on the materials used for the links and ends, maybe reducing capacity.
Rear suspension doesn't really change a lot. springs and shocks. Not a limiter
So if its done right, I'd say you could safely keep your rated towing capacity. Of course there's no one to turn to if it doesn't hold up.
_________________
2005 CRD "
Ol' Blue"
Red Ryder carbine-action, two hundred shot range model air rifle with a compass in the stock and this thing which tells time.
My build page- RL Komodo Rear and TJM Front Bumper, armored, lifted, JBA Steel D30, 4.10s and ARB air lockers.