There should be a small plaque near the top of the engine with the model you have? Forget the exact location but it should say what it is.

In case you can’t find the plate”

Here is a link to the W60 manual, with detailed diagrams and measurements: https://www.westerbeke.com/advanced%20specs/w60.pdf.

Here is the same for the W58. https://www.westerbeke.com/advanced%20specs/w58.pdf
Its dimensions and form are slightly different from those of the W60.

If you find out that your engine is a W60, hope you saw my earlier post about parting out our engine plus list of additional spare parts. Let me know if you are interested.