This is what i'm interpreting all that as (after a couple reads added with strange looks.... lol)
You've got an FJ40 which have bucket seats and a racing harness installed. The harness is mounted in such a way that the rear of your car can not be used and you would like to know if you can move the harness so that you can make use of the rear seats. Correct me if i'm wrong.
It's possible to move it but whether it's legal or not is a different story. From memory (which is a little scratchy) to have a racing harness legally mounted in a road car it has to be at a certain angle, 10 and 45 degrees come into mind. Either 10 degrees down from the horizontal or 45 degree from the vertical, that was mentioned to me from a friend.
Best bet is to call up a reputable store which stock race harnesses and ask them. One place is Revolution Race Gear. Blokes that work there are great guys and they have some awesome gear such as a hydraulic jacks which can get a car up in 3 pumps and can be carried by a 5 year old..... only cost $600...