I don't believe there were any ITRs in 95, but yes, an R tranny will swap right on. If you get a 96 spec, it'll come with a 4.40 FD and LSD. The 99 spec comes with a 4.785 FD and LSD. Both are hydro, so either one is equally feasible. As for cost-effectiveness, it would cost about $300 for a clutch, and about $800 for a Quaife LSD for your GSR tranny. A 96 spec ITR tranny would be about $1200, and a 99 spec would be about $1500. The OEM LSD in those trannies is pretty decent, but the Quaife is considerably stronger and will ultimately hold more power.