The spindle mount is installed on the Z-carriage from behind. To mount a different spindle it’s necessary to take the X/Z assembly apart, uninstall the current mount, install the other mount and put the X/Z assembly back together.
It would be nice to be able to install the spindle mount from the front, not from the back, to avoid all that hassle.
While it is not a full front mount, the EasyTram created by @Luke lets you adjust the side to side tramming from the front without having to remove the mount or spindle.