Macs are built as appliances.
Do you buy a fridge and go "hey can I change the compressor on my Korean built LG fridge to one of those new compressor units made by Daikin"?
Do you buy a car and go "hey I want to change my Honda engine to a Ferrari engine but still retain the body of the car"?
Why then do people keep asking "hey I bought a Mac and I want to change so-and-so component to some-other component?"
When the time comes to upgrade just put the whole computer one eBay (if it is still useful) or dump it into the trash and buy a new one. That's the Macintosh way. In fact my last line came from one of those Mac switcheur videos on YouTube, so you might want to look it up