Im rebuilding mine at the moment. Head is being done by turner engineering, and got a new set of rings an big end bearings for it. Thankfully the head and the pistons aren't cracked. The chaps at turners also told me that the rings may infact be fine even though the crank case pressure is high - apparently the engine is prone to building up carbon deposits above the first ring and behind it, preventing the transfer of combustion pressure into the ring grove, and basically jamming the rings to prevent a good seal.
Im changing them anyway as I have them out and have a new set of rings.
Other things to check is the the boost diaphragm is intact in the injector pump. Its a bit fiddly to get to but if you follow the pressure hose from the turbo to the injector pump, its under the cover where it connects to the pump. If its broken then the pump will not increase fueling when the boost pressure rises. It also causes your fuel tank to become pressurised as the turbo is pumping air into the fuel system under pressure!
Some people swap around the transfer box ratiosusing disco boxs etc to reduce revs at high speed. Ive done this -mainly as the box disintegrated in Lancashire and I needed to get back to the south coast and it was the only one I could find on a Sunday. Ive kept it as it seems to be slightly less noisy, and Im trying to keep the engine stress and temperature down to a minimum to extend its life.
Appart from that, change the oil every 4000 miles, and keep it cool (ive fitted a 76degreeC thermostat) and dont thrash it and it should look after you.
Also on the cooling side - you have to fill the system via the heater box hoses as otherwise you get an airlock if you fill via the raditor or header tank. Thenas the enengine warms up the thermostat suddenly opens and allows the air to clear, but bumps the water in the heater matrix onto an already overheated head (as it doesn't have any water in it) and the water then boils off filling the system with even more air until its suddenly half empty.