Direct answer: The two generations share part categories rather than part numbers. Rear exhaust section, intercooler tubing, intake filter, silicone hose and clamps are all offered for both, but each listing is written for one generation, so whether a specific number carries over has to be checked against that number.
For the 300, the catalogue carries rear exhaust entries such as RS15120 and RS16140-1, waterboxes such as RS16141 and RS16142, and intercooler and tubing listings written for the 300. For the 325, the tubing and intake listings carry the 325 name, including the 325 intercooler tubing upgrade kit and the 325 silicone power filter kit. That wording is where the two families part.
Only the neutral layer is shared outright: the 4 inch universal filter kits and the CUSTOM SIZE SS304 clamps, which are chosen by size. For anything else, give the model, the year and the number, and the fitment line decides. A 300 number should not be moved onto a 325 hull on the assumption that the engine layout carried over.
