As others have suggested, a pic or two would provide more to diagnose.

On my '72 MotoGR, going from a 28 in back to a 32 or 34 cog proved the limitations of the original Campy DR. So I found a 'donor' Fuji off which I borrowed its Suntour V-GT Luxe. That worked fine with the larger cog in back. Even with that though I got smoother shifting after I added a WolfTooth aluminum hanger & messed a little with the pesky B-Screw setting and chain length.