Having spent way too many hours on internet forums about Landcruisers, and our diesel one in particular, it transpires that the only real problem with the 1-HDT engine was a small production run of dodgy big end bearings. No one is entirely sure off when this was, and if it was isolated to Aus, but to play it safe we opted to change ours. There are aftermarket parts available from Aus and SA, but once you factor in shipping it is easier to just order from the stealership. The job in fact was very easy, most of the time was spent trying to take off the oil pan (think it has 27 bolts and is siliconed in place). Jack up the front of the car but let the axle hang down – enables you to take off the pan with the steering in place. Drain the oil – overnight is best. Remove the pan. Each conrod is held on by 2 stretch bolts – replace these as well. After changing all the bearings, torque the stretch bolts to OEM spec. Clean the pan, silicone and bolt in place. Fill with oil and the job is done. Can be done in under 4 hours, really.
Our oil pressure did not change significantly before or after. The old bearings actually looked fine, so we are carrying them with us as spare (hopefully wont need them because that would mean something big went). More peace of mind.