the lines are the same, flanges are the same. there is a slight difference in the R33 S1 and R33 S2 turbos, S1 has a steel comp wheel, S2 has a Nylon/plastic comp wheel. R34 turbos have the Nylon/plastic wheel and a larger OP6 exhaust housing. they all have ceramic turbine wheels.
the only thing you have to look out for when putting a r25 turbo on a 32 is, i believe that some of the older model 32's, 89 models have a different size oil or water line fitting, cant remember which one. someone else may be able to confirm this for me.
i had a 92 model 32 and it was a straight change over, all the fittings were the same size. the other thing to keep in mind is, if you dont get the turbo elbow with the turbo you will have to drill and tap a place for the wastegate actuator vacuum line nipple. and do some custom work to the 32 elbow to make it fit.