Hi Chappy,
I got the size of the Gin Pole from the h260.com site. I made mine to be 86" in total length. I used a 1"OD galvanized pipe and the wire rope is 3/16" diameter. From eyelet to eyelet the wire rope is about 18" long. I bought the parts at Home Depot and assembled myself. I used Stainless Steel parts and remember that the tag end on the eyelets needs to be crimped as shown in the picture (nut is opposite side of the tag). At the base, I drilled a hole in the pipe and then finnished off the birdsmouth shape with a grinder. Fit the shape as you grind to your mast base. The critical issue is that the birdsmouth is alighned with the wire rope. When you place the gin pole into the base of your mast, one eyelet on the wire rope is pointng towards the anchor locker and the other is pointing towards the mast. Therefor the hole you drill at the top of the pole for the wire rope to go through must be in the proper direction. I also placed some brass gromets to protect the wire when it passes through these holes. Hope this helps. Let me know if you have any questions.