Hello Tim you might be worrying a bit early about major rebuilds my 93 has near 100,000ks and I would not expect to do any thing to the bottom end other than internal chains and sprockets for at least another 150,000ks based on doing around 380,000ks on a Kawak 900 with out touching the bottom end and a couple of rebuilds on the top, GTR's are a bit diffrent in they have sliper bearings but if treated right should near do the same, keep the temperture constant and the oil good and do the chains as required and I think you will be suprise how long they will last I think the secret to geting big miles out of the 9 was never letting it idle while not moving and cooling, even sitting in traffic for more than 20 or 30 seconds I always turned it of to keep the rings tension in good nick, not so critical on a water cooled job but still something to keep in the head.