Am replacing the air cleaner bracket on my 1980 W116 300SD, and all three of the mounting bolts have "bunged-up" threads. Two of them had almost backed out of their mounts, probably from not being installed tightly the last time the job was done. Can someone please tell me the size and thread I need to purchase We have a serious looking industrial bolt supply house here locally, but would prefer knowing what to ask for as opposed to eyeballing for "close". I am speaking of the three bolts that attach the bracket to the engine. Thanks.

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1980 300SD 146K miles.