[MA70-3.0GT]

haha yeah suppose it's possible, although I don't think He'd be *that* surprised if the basic engine lasted that long as they're pretty solidly built apart from the head torque thing... But at 145k unless it's been neglected in the past or driven exceptionally hard I'd expect the bores/rings etc to be in great shape still

What makes you suspect it's tired, smoke/low compressions or just a suspicion? If the bottom end's fine I'd say perhaps just a head refresh with either a valve reseat or maybe just stem seals might be the way to go for it. On the throttle response you could maybe look into a modern VNT turbo or at the very least a roller bearing Garrett like you said, and isn't there something about using an N/A inlet or exhaust cam too? (not sure which one it was, or if it's even a myth maybe but I did read somewhere on here that one of the N/A cams is an improvement over the turbo one)