For fun, I can show you how to boil water with an ice-cube as a science experiment. Take a glass soda bottle with a good cap, fill it about 1/4 full of water, and put it in a pot of water on the stove. Now bring it to a boil so the water inside the soda bottle is boiling. Let it boil for a minute, so the bottle is well filled with steam. Turn the heat off and immediately cap the bottle. Take it out and let it cool down. This creates a vacuum inside the bottle. Now rub the top half of the bottle with an ice-cube. This really creates a vacuum inside the bottle, and the water in it starts boiling because of the vacuum.

I've done several conversions in the past without dumping and switching the oils, and a friend has done roughly a hundred of them over the years without incident. It really was on a lark that since I had the opportunity to do an oil swap that I did it. I probably wouldn't bother on a car that I was merely changing the refrigerant on. But if I was removing components, I would.

Your Weber is the two barrel downdraft unit right? That was oem on many cars back in the 70's and 80's. If you... Find one with a linkage that looks like yours, or something like yours, and you can combine parts to make it work on your truck.