Q: I HAVE 05 300 BASE WITH 2.7L ENGINE VIN R WHAT 3.5L ENGINE DO I LOOK FOR TO PUT IN FOR A SWAP?

There is no "direct" catalog interchange engine for your VIN because your present engine was installed at the factory with an engine specific computer(s), engine wiring harness, suspension (engine weights vary), and so forth. The alteration in weight will require suspension/alignment modifications that will have to be engineered. The carryover of the PCM and all controls (from the donor vehicle) must be comprehensive but even if you can get it to work, you might run into issues using the car legally. That is, you would have to confirm that the "new" vehicle configuration is certifiable insofar as Federal emissions law. Please see the relevant Federal EPA Engine Swap Guidance Document. California, and a few other jurisdictions, have additional requirements and, in the case of California, these are published in the California Engine Change Guidelines. Unless you have very sophisticated test equipment and a thorough understanding of what is allowed in an engine swap, you are much better off keeping the stock engine and, if need be, simply rebuilding it. Indeed, that is the advice stated up front on the California guidelines document. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.