I have had a few leaky old Ford radiators and the best fix is get it repaired.
The other methods are usually 'stop gap' measures and the problem comes back to bite when least expected.
I like the look of that extra metal in the 'A' crossmember. I've seen some crossmembers, modified as you describe, with cracks in the area where the metal was removed.
I ran duals on my pickup years ago on the original '47 flatmotor and had to change the power valves to a lower number to get it to run. They were 94s.
The intake manifold was one made here in Australia and it wouldn't run on one carb either. Both carbs need to be set up and tuned on the dual...