If indeed it had a pre-existing lower end noise, and the rest of this is new, that changes things a bit.

If the noise appeared at the same time, I'd say proceed with the timing chain repair and then see about the noise, it may well be related.

If the noise is in fact an older seperate noise, one that indicates other problems aside from the timing chain, cut your losses and buy an engine. Either a MBZ one, or a junkyard one that you will rebuild completely before putting in. Don't get a wrecking yard engine and put it in as-is, it will probably have the same timing chain guide issues in short order.

This will be expensive, probably more than the actual retail value of the car. Decide very carefully how you want to proceed, nothing is as bad as throwing several thousand dollars into a project, then realizing it will take several thousand more that you either don't have or don't want to spend. Then you end up selling the whole thing for a big loss and kicking yourself all the while.

Choose wisely...

MV