The 260E (aka 300E 2.6) had a 2.6 liter engine that made 158HP @5800rpm and 162lb-ft @4600rpm. It also had less standard features than the 300E. It was a bit slower as well.
The 2-valve per cyl 300E (M103) had a 3.0 liter engine that made 177HP @5700rpm and 188lb-ft @4400rpm. It had many more standard features befitting its higher status in the MB lineup.
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