Looks killer man . That clear oil level line gives me running over limbs anxiety but none the less sweet when checking levels. How did you adapt to the nissan stuff? I realize the nwf but they sell nissan adapters?
Im sure youve checked steering tow in but that sounds exactly like what you are describing. It would also be worth checking your wheelbase on both sides as well to make sure they match . Its possible at higher speeds if you have a link bar thats out of adjustment it would do some weird tracking...
The valve maybe worth looking into . I had a buddy that blocked the port off too. His put massive amounts of heat and his steering would try to lock up at anything above 20 mph . I think he had just a regular Saginaw pump too .