Larry
If it were mine and I could get the oversize pistons and rings and it only went up one oversize (or so) I would probably go with the overbore. I assume too, that the machine shop you have found has taken a close look at the existing liners and told you that you can get away with one or two oversizes and can give you a good bore. I have done it on a gasoline vehicle that was not a MB.
Jim

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Jim