hypothetically speaking, if were to find some junk yard engine parts off of a 2l 3 or 6, would i be able to install them on my cx-5?

 

This question is rather vague. Naturally many parts are interchangeable even if the updated part numbers do not superseded the old ones or are listed to fit. That kind of cross over and parts interchange information would be so large I cant even image who would want to under take the task putting it together.
The National Auto wreckers seem to have the best some what information on interchangeable parts. That's why they have the catagory "may fit but unconfirmed" on some of the parts offered for sale.

If a part mounts the same and function in the same capacity, sure it should work ! Common sence!