Andersen awning windows of late '50's

I have several old Andersen awning windows that have inoperable crank operators. Is it possible to replace the hardware with newer models since the exact replacement ones don't seem to be available? Does one have to remove parts of the sill to remove and replace the mechanism? Or should I just disconnect and install old style brass adjusters? This would mean removing the screen to open or close the window.

Here are two photos of a representative crank mechanism. You can see from the picture that the arms are about 11 inches. It looks like the mounting screws are about 4 inches or less apart. I cannot see any other screws, but there must be another or two holding the operator down. Any suggestions would be gratefully received.

Tom T.