With om 603 crank u will need shorter rods, low compression height pistons with really short skirt. Just short rods stock piston will hit the crank and is still over deck way too much. M111 piston and rod combo might work but i havent tested yet. Problably u will need to bore block too, i dont remember if m111 had same bore version. Short rod was i think in 2.0 and 2.3 versions.
Boost is the way to go.

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MB 300CE Turbo '88
MB 300E '86

This, outside of having a donor 3.6 car to swap everything from.

It is cool to have a 3.6 swap but boost can make far more power.

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90 300TE 4-M
Turbo 103, T3/T04E 50 trim
T04B cover .60 AR
Stage 3 turbine .63 AR
A2W I/C, 40 LB/HR
MS2E, 60-2 Direct Coil Control
3" Exh, AEM W/B O2
Underdrive Alt. and P/S Pulleys,
Vented Rear Discs, .034 Booster.
3.07 diffs 1st Gear Start

90 300CE 104.980
Milled & ported head, 10.3:1 compression
197° intake cam w/20° advancer
Tuned CIS ECU
4° ignition advance
PCS TCM2000, built 722.6
600W networked suction fan
Sportline sway bars
V8 rear subframe, Quaife ATB 3.06 diff

The AMG motor uses factory 145mm rods. It is a R/S ratio of 1.56. How short do you wanna go?

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1993 190E 2.6 Sportline

143mm rod and 30mm compression height piston, i know r/s issue, but thats best combo what i have found and might work, easy way would be full custom but i have no budget or intrest.
Right now everybody wants to sell me full m111, if i sourse pistons and rods and they will rotate, then there will be new thread.

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MB 300CE Turbo '88
MB 300E '86