Summary

The Prusacaster core part with corners slightly shaved to fit on an Ender 3 print bed.
coreender3v6.stl

Original found here: https://blog.prusa3d.com/the-prusacaster-how-to-design-and-3d-print-an-electric-guitar_71962/

Remixed from this remix "Prusacaster - Correctly placed hardware"
https://www.printables.com/en/model/412377-prusacaster-correctly-placed-hardware

Added a version to fit a 220 x 220 bed at user request. I don't know if this cut will compromise its strength. Split into 3 parts, glue them together, use lots of very strong glue. Use at your own risk.
core_220x220 1.stl
core_220x220 2.stl
core_220x220 3.stl

Update:
So,
Apparently the Ender3 suffers from quite drastic layer shift because the electronics overheat. As it takes 24 hours to print and it overheats around 18 hours in I sliced it lengthways into 3 parts (and a little bit to make it fit the bed).

MeshBody51.stl
MeshBody52.stl
MeshBody53.stl
MeshBodybit.stl

As always, Have fun!