My CB750 engine is now officially apart. I borrowed a valve spring compressor and got the valves off, so I can now take all the pieces to the media blaster.
The one thing that was in the back of my mind during this whole teardown was the broken intake. I had accidentally cracked it a few years ago. I thought I migh be able to carefully chisel it out. That was a no go. Then I tried JB Welding in a screwdriver to bond it to the manifold and twist it out. That failed miserably. Finally, I just went Neanderthal on it and chiseled it out the easy way. There was no way this thing was going to unscrew as it was glued in good and solid. I took a dremel and ground it smooth. I will just permanently bond the replacement manifold in. I just need to find a good bonding agent. But first off to the media blaster next week.