Classic 911 or 912 refurbs

[Chemical Ali]

Looking at getting a piece of pork history. Is it essential to stay as factory or do "upgraded" examples hold their value the same?

Ive looked at a few and most have been refurbed to some degree, some with modernised parts, some with original parts. How does this affect value?

[SRT Hellcat]

Blue chip stuff is a mint completely original S model. 2.2 or 2.4