That was done by us a long time ago , way before Uprev was in the UK.
Strange it has had HKS head gasket's fitted thou.
It was a nice car when we last saw the car.
Yeah, I thought that strange "The essential head gasket upgrade" I've not heard of anyone else with a Vortech needing that?
Regarding longevity and mileage, no hard and fast rule. It's obviously had the best chance being fitted and tuned at Abbey in the first place and appears to have been well maintained. The V3 has it's own oil reservoir so oil needs changing separately from the engine oil. I would be checking the service history/looking for evidence of that, as a normal garage wouldn't change it unless asked to.
My main concern would be why and when the head gasket was changed as this wouldn't normally need doing with the relatively low boost produced by the Vortech so could have been a failure at some point. Has the pulley been changed for more boost or is it the stock 3.33" ??
Have a read over on my350z.com, there are loads of threads about reliability and mileage...there are cars that blow at just a few thousand miles (usually a bad tune) and those that are set up nicely can do 150k +