Very cool project! I hope you do the keyboard too, because (in my opinion) that's the worst part of the C64. I see you're building the C64C form factor. I don't know if that has a different keyboard than the bread bin I have, so maybe yours already has a better typing experience than mine. And even if it's the same keyboard, the lower profile of the case must already make a huge difference. But building a nice keyboard for it with good switches will still make a big difference.
I'll definitely do the keyboard, actually I'm using the breadbin keyboard here because I think it looks neat. Commodore were pretty good at keeping things compatible. The motherboard was intended for breadbin as well, but fits fine in the C case.
How do you like typing on it? I wonder if I dislike typing on my breadbin only because of the height of the case, and the position it puts my wrists in.
I find it perfectly fine and acceptable for long periods of time, I think the original keyboard is quite good mechanically (springed keys with conductive rubber feet onto pcb pads), the ergonomics of the breadbin (I have an ultimate64 and a few real ones) is not my cup of tea, it ends up hurting my wrists after longer sessions, no such problem at all on the C64c models.