Only 32k miles, but stored for 20 years..., How far should I take the Engine apart? Options

[dsmeyer]

My project is a bone stock 914 2.0 that was stored for almost 20 years.
The Silver paint is bad but it has only minor surface rust on the battery tray and
a couple other spots.

I have stripped the car completely for paint work and plan to restore and, or rebuild
everything before it goes back on the car.

My question is, how far should I take the Engine and Transmission apart?
The Engine turns over freely by hand.

I would like a McMark Engine, but I would also like to keep the stock fuel injection.
Maybe 1/2 a McMark Engine with stock fuel injection. Would it be worth it?
1/2 meaning I may only get half the power increase with stock fuel injection.

My old 150k 2.0 is stock other than "Euro" flat top pistons and was great for
many, many years, but a little extra power would be nice.

The least I would do is take it down to the short block and just replace the pistons
and cylinders and rebuild the heads if needed.
The most I would do is McMark engine with stock fuel injection.

I would really like to hear what the Engine Experts on this forum would recommend.

As for the Transmission, should I just change the oil and run it, or take it apart and
give it a good cleaning and inspection inside?