Hi Tony,
I have both a '79 450SL and a '82 380SL with 560 engine and trans installed... I've been using the '82 as a daily driver for almost a year now and am very happy with it. It gets close to 21 mpg, and is a hoot to drive with the big engine installed. No maintenance problems so far, but I do need to replace the disc pads soon. (I'm letting my daughter use my '82 300D as it gets over twice the mileage of her Range Rover!) (Also, don't want to drive the red '79 450SL in the rain... since the '82 needs paint, it's the logical choice.)

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Richard Wooldridge
'01 ML320
'82 300D 4.3L V6/T700R4 conversion
'82 380SL, '86 560SL engine/trans. installed
'79 450SL, digital servo update
'75 280C