well people i found out today that the 1976 model 120y diff is useless to try to get it in the 1200 its mounts are different the pinion yoke is to big for the tailshaft to bolt up to wat i did find is the 120y centre is much bigger than the 1200 so in theory it may be stronger so unless u get the tailshaft out of the 120y and get it mated up to the tail shaft in mine its no good oh well some times u have to learn the hard way looks like its the 31 skyline to be cut down.