It used to be a bit of a common thing with them,mine tracked badly to the left on a certain stretch of road.
As said alignment check and also check the brackets holding the twin antiroll bar set up arent cracked or broken,even that they look in a similar place both sides as that was a cause on another one I owned.
I think there's a company making spares now as I couldn't get them from ford back in 1998 and had them made up in work.
Also big wheels and extensive lowering don't help either,not saying yours is but worth noting.