Well, I finished this project and I remove ~ 5.5 lb from the manifold. Aluminum weights ~.10 lb per Cu In so, I removed about 55 Cu In of material or a block that would be a 3.8" cube.
The numbers written near the dist, are the weight of the bare manifold 20.06 and the weight of it assembled, 24.6. The manifold bare, weighed 25 lb before I started.
I made a change, on the bottom since I last took pictures. I had done the area of the push rods holes, with a 1" ball end mill but, 3 different cuts of 2 different depths (center the deepest). Overall, it looked like one radius, so, I grabbed a 1 3/8 ball end mill and placed in the cuts and it look pretty good so, I chucked it up and the final cut is 7/8 deep (from the bottom edges of the manifold), with that 1 3/8 ball end mill. The minimum port thickness, in that area is .33 so, there is plenty left.
I took .210 total, off the bottom of the manifold, back to the rear of the inspection cover, behind that, I took .110, to the china wall sealing area.
I also included a picture of the holding fixture, again made from scrape it had. They are 1.13 thick pieces, I keyed the bottom, to again fit my table slots, with 1/2 x 13 bolts, C'bored into the aluminum. Most Bridgeport type table slots, are on exactly 2.500 centers so, I can reuse them w/o changing the machine work on them. There is .002 clearance on the sides and .005 from end to end. That way, there is minimal clamping force needed to hold the manifold ridged.
Next up, is the Weiand TP manifold base, it weighs over 16 lb. I can't really do anything with the top, even though it's twice as heavy as the base, with both carbs, it's 33 lb.