Hi Tim
Have spoken to a jeep expert mate for you ,like most old vehicles there is alot of play at the steering wheel even when the box is OK. It is possible to adjust the steering box,there is screw and lock nut on the left hand side of the box but you have to be very careful when adjusting it or the casing will break in use.The method is to jack up the front of the vehicle ,tighten the adjuster then move the steering GENTLY to full lock ,
if the steering tightens as it gets towards full lock it is over adjusted and must be backed off. When on full lock there still needs to be a small amount of play at the steering wheel rim. As I have said before on the forum the average MOT tester does not understand old vehicles and will fail things which, in effect, they do not know about. Ask around and find a tester who is used to older Land Rovers as they have very similar characteristics. Hope this is some help to you but if you want to speak to
Rob if you let me know I will PM his phone no to you. He will gladly help you in any way he can.
Cheers
Degsy