Almost to your specification:
You would have to bush the 40 tooth gear.
20T, 1" face, 3/4" bore. Stock #6867K75 $46.23
40T, 1" face, 7/8" bore. Stock #6867K82 $91.63
These are for finished bores (keyway and set screw). Prices are about a third cheaper if you get plain bores.
Weston Bye - Author, The Mechatronist column, Digital Machinist magazine
~Practitioner of the Electromechanical Arts~
Theory & Practice-
Theory is when you know something but it doesn't work.
Practice is when something works but you don't know why.
It it dangerous to combine Theory & Practice;
nothing works and you don't know why.