The rings will interchange but but they are drilled in different spots for the fixing hardware.So you can create your own 43t on up rings by drill press and file method. It might be noticeable from the inside but for a rider it shouldn't be an issue. I remember Bicycle Classics offered these 44t (or was it 43t) at one time
BOB FREITAS liquid sunshine here in MILL VALLEY, CA USA
ex employee of the Bike Spot in Santa Clara which originally was his Grandfathers Blacksmith shop