I found the files on Thingiverse and printed them for a friend. It is a working model engine (35% scaled) with parts color-coded... Sort of. It's really cool!
This is NOT my original design, it is a make from Thingiverse. I do not know this site's policy about posting makes versus original designs. If I am doing something wrong, please let me know!
EDIT: An issue was brought up in the comments that I think I should address. The gcode files provided are for my own profiles and settings, which were changed throughout the build; theoretically, they should all work with a MMU2 or MMU2S, but the profiles are slightly different. They are based off "Optimal MK3" from back in the day but with a slower and slightly thicker first layer and slower infill.
EDIT 2: I should've figured this out earlier. I added the STL files from the original model. That way you can slice the models with their own preferences instead of having to use mine, especially if you don't have the MMU2(S) upgrade.
I highly recommend you slice the STL files provided as they will go through whatever profile fits your own printer the best.
More instructions about how to print and assemble the engine can be found here: https://www.thingiverse.com/thing:2451310
Most parts should be printed with brims to ensure optimal quality, and sanding might be required to have parts stick together. My printer was in a cold room so that might have contributed to warping.
The user re-uploaded this model. The user is not the original author of the model.