casement window mechanism

Folks we need casement window mechanical opening replacements. The attached photo shows the 30637. It seems odd that the 6" linkage arm is permanently riveted to the 30637 arm, instead of being able to replace or interchange arm lengths. Since all parts or riveted this entire unit must be replaceable? The part # on the screw cam says 30471. Note the screw cam in in the center of unit (it may not matter if we can get the rest to work.)

Note these window are nearly 30 years old. Windows are fine, we need to replace the hardware for right hand and left hand opening windows. ALL have the same length link (6") . The difference is the part # 36036 or 30637.

Rick