If it is like my '94: Take the headrests off, pull up on the bench seats using the black handles provided, they should be split, then pull the backrests forward and align the hole in the headrest with the pins on the bench seat. Provides about 88 cubic feet of room I don't think there is anything bigger around.

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dtf
1994 E320 Wagon (Died @ 308,669 miles)
1995 E300 Diesel (228,000)
1999 E300 Turbodiesel ( died @ 255,000)
2006 Toyota Tundra SR5 AC 4X4 (115,000 miles) rusted frame - sold to chop shop
2011 Audi A4 Avant (165,000 miles) Seized engine - donated to Salvation Army
BMW 330 xi 6 speed manual (175,034 miles)
2014 E350 4Matic Wagon 128,000 miles
2018 Dodge Ram 21,000 miles