I think the oil pump's chain/sprocket is in front of the timing chain/sprocket on crankshaft, preventing you from easily installing an endless chain even if you remove the lower timing cover.

Also, if you remove the lower timing chain cover, it will be a good idea to replace the front main seal.

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1986 300E (3/2002) Rear ended and totaled (10/2009)
2000 Xterra (5/2000)
1992 400E (11/2009) -Sold
1986 300E (12/2009) - Sold
2004 E500 Wagon (6/2013) - Sold