I got on this kick starting about 20 years ago when I wanted to figure out why all restored A's I drove were gutless compared to unmolested originals. After tracking it to the cam I began studying A @ B cams as well as cams in general. The pieces of the puzzle have just been falling into place the last few years.
Physical limitations make it impossible to regrind a used cam to regain lift without increasing duration. It can't be done. The greater the lift the greater the duration. It's just a fact of life. Increasing duration past a given point reduces low end torque. I don't know yet where that point is, but don't think you can go much beyond the duration of the factory "B" grind without reducing low end torque. The horse power curve will move upward along with the torque curve. However with all else being equal, maximum torque will be reduced.
This image is a copy of Ford's original horsepower and torque chart for the Model A engine. I took the data from Ron Kelley's dyno test of a "stock" Model A engine and plotted it on the chart for comparison. The camshaft in the engine is a typical "stock A" regrind. The results show what I explained above and was not unexpected. Stock regrinds typically include a compromise of reduced lift and expanded duration so neither is too extreme. Comparing the torque values clearly shows why the typical restored "A" is relatively gutless.
See: Ron Kelley Tests the Model 'A' Ford Engine
Here I've simply added the Model B as well as some of Ron's "upgraded" Model A tests for comparison. This is only horsepower which really is less of an issue than the torque. I need to do the same with the torque specs to show the full impact.