Lehman Manifold
Greetings Polecat 702 and welcome to the forum as well! I went through similar search for my same Lehman last Spring when I removed my exhaust manifold elbow to fit in a new fuel tank, then proceeded to jam a screwdriver through the bottom of the elbow.... luckily, Brian at ADC had a replacement for me but when the main exhaust/intake manifold had the same issue.... rotted out at the bottom..... Brian put me on a "wait list", so I recommend you get on that list. Per above, Brian has a foundry cast the manifold but he does the machining on the mating surfaces. Search under "Lehman Manifold" and you will find my story, along with some reasonable photos. Long story short, I located a welder in my region (NY) that specializes in repair of vintage diesel engines and they did a fine job repairing my burn through hole with silicon bronze. One season down but they claimed their repair would outlast the manifold and they did seem to know what they were doing there. At this point, I have not heard from Brian, and I assume that I am still on the list. I had contemplated grabbing new from him when it became available, but may bail on it as well. Get you name on the list is probably best as you explore other options. Out in Las Vegas, not sure of your access to welding options but take a look at my prior posting re: this topic and see if it might be a direction for you, at least as interim. Good Luck!