My wall is framed with 2X3, and all pocket doors frames are 2X4. Is there a easy way to change the framing with out taking the wall down

Could yo have it flush on one side and fill other wall to flush. Double 1/2 inch drywall?
If you are lucky, 1 side may have a short wall.

If wall is unfinished, u can add 2x4 along side of 2x3.

Or u can scab 2x3 with 1/4 ply and 1x2.

Chuck