We recently bought another 08 LR3 from a luxury dealership and I had a chance to chat with their LR tech, who they stole fair and square from a dealership, and he relayed his opinions on the whole engine thing.
He really likes the 4.4, has great faith in it, it's about as bulletproof as an engine gets. He services 4.4's with 275K miles on them, and they need oil and filter and the usual maintenance items, nothing more. He's not so fond of the 5.0, he feels it is prone to sudden failures of the water pump and the usual failures of the timing chain tensioners, also he's not a huge fan of the SC engines. His own vehicles are running 4.4's, and he is of the opinion that the LR3 will start to gain a following because of the bulletproof drivetrain.
If your 4.4 does manage to die, or you wear it out, they are really comparatively inexpensive at the local boneyards or ebay, because their isn't that much demand for them. A local guy ***** out his LR3 and has dropped the asking price on his motor and transmission, obviously not much interest in them. I tought about buying it snd keeping it as a reserve but why bother? The $1600 he wants buys a lot of oil and filters.
I have also wondered about a turbo or supercharger for a bit more power, the beast is fast enough for normal driving, it feels quicker than our old Suburban with the 5.3.
And now the crazy part-I like the 4.4 so much that I am seriously thinking of finding a donor LR3 or such and transplanting the drivetrain into my 79 Squarebody to replace the tired 5.7 . That would give me almost twice the HP of that poor old smogged out SBC.