I' trying to setup a way so that some phones i have on my shop floor cant be used to call outside the company. I want them to be only internal phones.

Is there a way to make a preference group that can do this or maybe some type of outside line blocking group?

This feature is under the Dial Plan. You'll want to create a Service Group for the shop phones, assign those Call Appearances to it. You may need to use a Restrictions list or don't add any Outside Lines to the Service Group. They should still be able to dial internal extensions.