Why not just use a 616 flywheel? They are lighter than the 617 flywheel by a few pounds. The 617 flywheels are relatively rare so you could probably sell it for more than a 616 flywheel would cost.

Most of the people who have done the manual conversion have used the lighter 240D flywheel with no ill effects.

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine