Point gap of 0.020 s/b correct for Fairbanks Morse Magneto. What are numbers on Magneto - I think a 44 ZTU original s/b FMK4B4.
That decodes as follows: FM = Fairbanks-Morse; K = basic design (with disc rotor under a one-piece top as opposed to later J or X models that had removable rotors under separate caps); 4 = 4 cyl; B = flange mount or A = base mount; 4 = MM Application with 25 degree preset - other numbers indicate other tractor brands potentially with different Presets. (3 = AC, 7 = Continental, 11 = IH, 73 = Ford 2N?) As I understand it the Preset is essentially a built in fixed advance.
Other magnetos can be and often are swapped in - As I understand it, the later FMJ4B4 or FMX4B4 should be direct interchange for MM with same 25 degree preset. Other mags such as the FMX4B3 built for Allis Chalmers will work but Preset is 30 degrees instead of 25 degrees. The FMX4B3 works fine - I just put one in a ZTS in place of the original FMK4B4. I believe there were other applications which had Presets as low as 15 degrees. Not sure how, but I understand the presets can be changed if you know what you are doing, but not sure I would mess with it.
Why do you say you have timing problems - does it not run good or are you checking with a timing light? If it runs good, I'd leave it alone.