hello my first post here
q1 is there any 3d printable full size cases
I believe it's been done before, but don't know if files have been released. The ones I've seen have been assembled from several smaller prints, rather than printed full-size. Easiest would likely to be a tray case, either for PCB-mount switches, or to be compatible with an existing plate. 3D printed plates have also been done, but they tend to be thicker than spec for MX-compatible switches, which makes mounting much more difficult, and you can run into PCB clearance issues if you're not careful.
A quick search comes up with a bunch of results for 60% tray cases, which it appears can be fit on a larger sized print bed to print in one piece, here's one example:
https://geekhack.org/index.php?topic=91080.0q2 is there a standoff layot standard on full size kb's
Not to my knowledge. Other bits are nonstandard as well -- for instance, the spacing between 'blocks' (e.g. gap between number row and f-key row, gap between alphas and nav cluster), and the position of the USB cutout.
If you're looking at doing a 3D printed case, I'd look at the different aftermarket PCBs available, pick one you like, and do your design based on that board's measurements. I'm not sure off the top of my head where to even find a 104 aftermarket PCB though, perhaps someone else will know.