For those of us with the Westerbeke 40 engine, these are the same as the Perkins 4.108/4.107. Sometimes you can find the Perkins parts cheaper that getting them for the W. There is a web site that compares the parts prices between Torrensen and TA Diesel at
www.sltf.com/boat/system/engine/EngineParts.htm, not sure how old the prices are. Foley's engines has rebuilt Perkins 4.108 engines for sale and will exchange your dead engine and give you credit on the usable parts on the old engine. To get the credit you have to build a cradle on a pallet and ship to them before you know what credit you will get.