I've got a '92 960 approaching 200K miles and it's been more reliable than the tried and true '86 760T it replaced. There has been some discussion about the blocks leaking on early 960s but my hunch is that this is more related to poor maintenance than anything else. I'm pretty sure Volvo didn't indicate service intervals for coolant replacement in the early 960s...which is a big no-no on an all aluminum engine. If an owner followed this "advice" they were bound to experience leaks in the block. In any case, the blocks all started leaking fairly early in the cars' lives (by 100K miles), so if you find one that doesn't leak then you should be fine. Aside from that, the early 960s are essentially 760 turbos with a different engine and transmission so the remainder of the car is bulletproof.
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Lance '92 965 w/ 180K miles