The used cam can be installed if it meets the following criteria:

1. The cam is healthy with no scuffing.
2. The cam and matching followers are all replaced.
3. The cam and followers are all in their exact respective locations in your engine, they cannot be jumbled during the transfer.

Beyond that, I'd worry about what caused the initial failure. What was the failure pattern?... all intake lobes?... all near one end of the engine?... random?

I'm not exactly familiar with the M103. How are the lobes lubricated? I'd look for oil starvation in the form of plugged oil passages and try to remedy that.

One tip on installing the cam. Mark everything and make sure eveything is in sync. I like to turn the crank to 0° then mark the cam sprocket at some logical place so the replacement cam will go in the same way.

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95 E320 Cabriolet, 169K