See, this is where it goes all sideways.
I have a 44 year old truck. I get the collecting cars thing. I understand the collecting old guns thing. I get the being creative and building your own furniture thing. But he's not collecting old computers and keeping them alive. He's making a copy of the old machine using a new one, that acts somewhat like (but will never behave exactly like) the old one. The guy's creating yet another emulator using an ARM processor board.
Car analogy again: my truck has the original engine castings. It's basically an 1970 LT1 engine, tuned for truck use, which makes it doubly cool; but, it's still the original castings. It's still carbureted. It still has the mechanical voltage regulator. It's as original as I can make it, reasonably speaking (the A/C may need to be upgraded because R-12 is damned hard to find and expensive). If he wanted to do it right, he'd start with an actual C64 or at least with a 6510 processor, which might require he make one...
Since I work for an automotive OEM.... When this is done, there is an Engineering Change Order documenting the change and why it was implemented. We don't change anything without first getting the approval of the customer; and, invariably they will want all the relevant DV and PV testing redone. Huge effort and pain. All of this is well documented and nothing ships until we have final approval from the customer.
The part number may not change; but, the part revision level will. PN 123456 RevA will become PN 123456 RevB. We treat it as the "same" part number but will only ship the latest revision once we have customer approval. As for tracking, I don't know how our customers tracks the change internally; but, I can tell you which batch, serial number, and date code the new revision started shipping.
It won't go down like that.... It'll be more like
scientist: Oh no! there's a 5 km asteroid going to hit us in 150 days."
Politician: How do I know you're right? You've been wrong in the past. Earth has never been hit by an asteroid, not in my lifetime or the lifetime of my father's father's father. I don't believe you."
one week later
Scientist: We've projected the orbit and can confirm with 99.99% certainty the asteroid will strike the Earth on the west coast of Africa in 139 days at exactly 10:43pm EST. It's 4.2 km and when it strikes it will be a civilization ending event, killing a projected 83% of the human population unless you fund the rocket we need to stop it.
Politician: So, you're not 100% certain? And you're saying it might strike Africa. And I thought you said it was only 5 km. Now you're saying it's 4.2km. You all don't even know how big this thing is... How much is the rocket going to cost? Do you have any idea what percentage of the U.S. GDP that is!? That's U.S. taxpayer money you're talking about. I think you might be wrong about the collision. You all were wrong about that asteroid... Apo something, right? Why should we agree to spend American taxpayer's money to stop a rock that may strike Africa. That's on the other side of the Atlantic ocean, half a world away. You scientists just don't know what you're talking about with your heads in the clouds looking at your stars all the time. You need to get down to Earth with the rest of us regular folks and do something useful.