The original Modulcaster core part split to fit smaller printers and reinforced with two 8mm steel rods.
There're different bridge files: original modulcaster one to fit Harley Benton bridge and altered one to fit Musiclily MX0823CR bridge, which has different pickup and mounting holes spacing.
If unsure - print the top 2mm of each bridge model (e.g. shift the model -43mm on Z axis, to place it mostly below the bed level) and use it as a stencil to check which model will fit your actual hardware. Feel free to request new model changes if your bridge is not supported.
READ CAREFULLY: These rods are not intended to be screwed in, but rather glued in with epoxy. If you intend to use M8 threaded rods you will probably have hard times inserting rods: try full assembly before applying glue. In case you have issues with tolerances and cannot fit your rod into printed holes - either drill out holes to wider diameter or use different rods (e.g. use smooth 8mm rods or M7 threaded rods). Depending on the wall count and top-bottom layer count of your print drilling might not be a good option - using thinner rod with more epoxy might be a better choice.
2024.03.18 UPDATE: The neck part of split core now has cavity extended to accepth humbucker. The original cavity is shifted 2mm towards the bridge to make the pickguard screw hole usable - this may (or may not) affect how the tele pickup fits the cavity when mounted on the pickguard.
2024.03.22 UPDATE: Uploaded the bridge part adapted for 78mm x 43mm short fixed tailpiece with 3/5 screws mount, 33.5mm apart. It features humbucker cavity and holes to install humbucker mounting plate.
2024.03.24 UPDATE: Added mount holes to the humbucker bridge part for 73mm x 40mm short fixed tailpiece with 3/5 screws mount, 21mm apart.
The author remixed this model.
Split the model in broken line and added bores for steel rod inserts