The 460 top is not power. I dont think the 463 power top can be adapted, not that you need it. The grill can be changed but I think then you have to change the bumper and headlights too to complete the makeover, not really worth $$$$. Obviously on the 460 maintaince will be higher. The engine is more ore less the same, yes, but there are a lot more things in the driveline the can fail (not that they will) and these are more expensive parts than for your SD. Things like brake rotors/pads, bearings, diff locks and related hydraulics, trasfer case, and seals for all these things will need attention on a 20 year old car so just keep that in mind. Used parts are few and far between but can be had. Once you get it sorted out it should be good.

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2006 E320 CDI
1998 S320
1987 190E 2.3-16

1990 300D 2.5 Turbo(sold)
1987 300SDL Turbo(sold)
1987 300TD Turbo(sold)
1987 190D 2.5 Turbo 5sp(sold)
1985 190E 2.3-16(sold)
1984 500SEC(sold)
1984 230TE(sold)
1978 240D(sold)-Miss it!
1972 280SE 4.5(sold)