1- Wich model fit my Xcarve:
2- Why 8" of travel ?:
It's for the upper side, if you use long toolings with this option you should be able to clear the bottom of the sider with the tool tip.
3- Why a longer front plate ?:
If you use extra short toolings and you have Y risers, with this option you should be able to touch the wast board with the tool tip.
4- Can I reuse my original Z stepper motor:
Yes you can, you need to remove the pulley on it. Some have a pressed pulley and other with set screws. If your pulley is pressed you can remove it with a puller, cut it with a zip cut or any other method!! You can do a search about that on the Xcarve forum for more examples!!
You can upgrade to a bigger motor like this one: 269oz-in stepper
Maybe it's time to upgrade all your axis with the bigger motor!!
5- Is it a difficult task to upgrade my Z axis:
No, for most our Z axis model, you only need to remove the original slider parts, remove all the V-wheels and the acetal nut from the spindle mount.
Mount the new slider to the X carriage and mount the spindle mount to the front plate of the new slider.
For the bolton slider you will need to keep some parts of your original one.
** Maybe you will need to extend some wires for the motor.
After the mechanical you need to upgrade your GRBL settings, here a good starting point:
$0=10 you can reverse the Z direction in the Machine set-up if you use easel or you can Re-wire your stepper. Only to swap to wires of one phase.
** If your Z axis is reversed,
** For better performance you can change your hardware microstep setting to 1/8 and re-adjust the setting $102. Your Z axis will run better without a loud noise.