Here is the set up for machining out the old valve guide. I dialed in the outside diameter of the o.g. guide and locked in my mill, then I machined it out and drilled and tapped the head for a 9-16 18 tap. After this set up, I had to flip the cylinder around and mill out the piece of metal that was still in the combustion chamber. I also spent an hour polishing the bases of the cylinders and the wall. They glow like diamonds and look amazing. It is pretty close to the o.g. plating on my original spacke cylinders.
HEre is a pic of the valve guide being threaded. We were able to modify big twin sidevalve valve guides from rowe. They are made out of cast iron which is ideal.
Here is a pic of the modified valve guide next to the donor one. This is a fix that my friend Steve recommended, and I think that it makes a lot of sense, The cylinder does not have very much meat to it after machining, so I would be a little apprehensive of a pressed in valve guide. I will give this a try and hopefully it will be a trouble free fix.