This pic is from someone elses thread along time ago. From what I remember they were different pre-chambers. There should be different the Numbers on the chambers rims.

Also in the 2 pictures posted by the OP it looks like the retaining rings are distorted because someone did not use the correct tool to install and remove them.

However as other said be sure the old heat shield is gone.

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84 300D, 82 Volvo 244Gl Diesel