No it isnt a gtr. Its a gts4 with a built 26 conversion making over 400 wasps atw's.
lived and worked locally until recently. Farkin tuff car but definitely a hoon.
Now that I cant help you with. what I can tell you to assist with I.d. is that it has a lever on either side of the rail with a brass knob on the end. these levers are lifted to the verticval position to slide the rail and back to the horizontal to lock it in place.
wish my car was here and not at the workshop so i could actually go measure.
From memory about 25/30 mil. You can also rake the seat back a bit to give yourself more head room by going to a lower slot on the back.
None at all, when I got around to doing the cage I had to cut the rail that seperates both side rails so the seat could go down a slot or 2. Its pretty basic stuff mate.