Jim,
I was reading a link Mo posted on rigging, your gin pole is also referred to there as a pole derrick or dutchman.
I was experimenting with alot of things on my shop. This is a redneck lifting engine I was playing with, some old Lowes store racking. I assembled the first pair of racks, cable braced it and attached an axle between them. This is a shot from the end with a windlass attached on the axle.
An old motor grader blade made a brake that we could drop behind a handle. I then loaded it with rocks as a counterweight.
After we lifted a bent I added another section of rack and rigged it further forward.
I've also seen a pictures of a gin that looked like a tapered apple picking ladder with a windlass at the base.