Haven't done this before, so let's see if this works. http://www.flickr.com/photos/11328950@N07/sets/72157601791481680/

Early 77 W123's had the same low mounted filter as the W115.

JimmyL had one.

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So either it's a replacement engine or they pulled an engine way back off the shelf when they installed it on 79.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

I'm gonna go with it's a replacement Guess I'm back to getting my current block rebuilt.