From what I've heard, those lower ends on the 4.5 will outlast everything else on the car. As long as they've never been run short on oil, poor drain intervals, overheating etc.

__________________
63 220S W111
76 300D W115
2013 VW JSW TDI M6

previously-
73 280 SEL 4.5
86 300E 5 speed
2010 VW Jetta TDI M6