Thanks folks,
I have the replacement straps already cut out and hole punched. The 4 screws that were in the pedal ends were pretty easy to get out and they cleaned up great (round head steel screws with brass washers) but I have only been able to remove 1 of the 4 screws on the cylinder ends so far. Patience... Patience...
So my research seems to indicate that this pedal assembly is an aftermarket option. A dealer friend has has about 8 machines or so in 40+ years that have had a variant of the two pedal design. none exactly like this, but similar.
Since the original owners immigrated from Germany, bought a home in SF and immediately went out and bought a mother of pearl Singer treadle, I am guessing that $$$ was not an issue. so getting this "upgrade" seems consistent with the existing history.
Of course my friends viewpoint is that it adds at least 20% to the value.... hehe