I couldn’t find a data sheet on those motors. I did find a few images. They are larger than they need to be and the gShield will not be able to get the full potential out of them. It is unlikely it will fit on the Z axis, but they will probably work on the other axes. If they are 8 wire motors you will need to connect correctly. See this blog post.
Bottom Line: I would not recommend them, especially with a gShield, but if you have them already, you can probably get them to work.
It’s a pitty, I don’t want to mess around to much with the design. I need to buy a machine, put it together and it must work. Then afterwards I can modify things.