So any Gen 1 (up to 1985) W126 booster will accept any M/C from a gen 1 W126 or even a W123, *without ABS*
The Gen 2 boosters like in the SDL will look drastically different and as far as i know, will not work with the gen1 equipment. As for the M/C VIN # split, the boosters are nearly identical even after the split. I have a booster from a 75,000 model and the pre 56,000 booster is identical. The only difference will be slight difference in pedal feel/ travel based on bore size for the M/C you choose, which beyond factory OEM, is really based on personal preference/ budget.

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