[KevinH1990]

I suggest that you check this link for information about the stock 987 radios:

https://www.boxa.net/topic/60003-how-to-install-double-din-to-987/ (This is the UK Boxster site. You may need to register to read the thread, but it is free.)

If you can post a photo of the back of a 987 radio, that may show how the connections work. You will need to figure out the speaker wire connections, power (both constant and switched) antenna and illumination. If I were to do this, I think I would need to buy the after-market wiring harness adapters for both a 987 and 986 and then interconnect the car-side of the 986 adapter with the radio side of the 987 adapter.

I probably wouldn't be able to tell whether it was simple until I completed the work.

The biggest potential barriers are (1) if the 987 radio uses fiber optic connectors and (2) if some type of canbus communication is needed for the 987 radio. If you can verify that those issues won't affect your installation, and the price is right it seems like this is a low risk/high reward scenario.