The mesh with the changewheels looks 'right', so on that basis are of the same form, 20DP with a 14.5PA..
The small gear is 5/8" (16mm) thick, the larger one narrower (because it has to fit between the large pulley and bullgear) looks to be a nominal 7/16" – mine came out at 11.76mm with calipers..
I can't measure the diameters because the gears are in situ, but you should be able to calculate the OD for the blank from the toothcount and DP – er, 56+2, divided by 20 = 2.9"?.. …21+2 divided by 20 = 1.15".. ..assuming DP is indeed 20.
I'm not sure what or whether any allowance need be made for running clearance?
..It would be useful if someone else would check and confirm or correct this post if necessary..
I'm fairly sure the original gears are in cast iron, as per the changewheels.