Believing that the overdrive fifth gear ratio for the automatic is 0.83 and that the revs per mile for the E-300 diesel are approximately 2100 rpm, working backwards, one could figure that the rear end ratio is 3.07?

Crawling under and wiping the accumulated grim off a certain spot on the third member confirms that!

Using 814 revs per mile for the 215/55X16 Michelin MXV4s,

814 X 3.07 X 0.83 = 2074 revs per mile.

Wonder how the diesel would like the 2.82s or whatever is in the E-420/430 V8s?