Merchev check out- 4×4 Labs. These guys are making conversion flywheels/adapters for sbc bolt patterns, and the flywheels are supposed to be externally balanced to match the balancing of the MB torque converter. When I get back home, I can cut/paste a link for you or PM you the link that discusses this problem in depth- its on a diesel conversion forum.

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1984 W123 300D turbo
1989 SRW F-350 Reg. cab 4X4 &7.3 w/ Banks turbo
1993 Cherokee 2dr 2wd w/ 4.0 L6
2007 20ft Tiger car hauler trailer

thanks Farmfuel, the kit i got came with a flywheel, spacer and a starter, but I think i'm gonna give up on the 617 and go with a cummins.