Those 1-32" twists back then had a little deeper groove. The best sabot remedy for them were a little heavier bullet. I recommend trying T/C Shockwaves 300 grain & Harvester sabot/bullets in 300 grain for best fit. If you live near a Cabelas, Precision-packaged bullets like the Dead Center in 340 grain would be my first choice to try.

Just my opinion on what's best for that rifle... others may vary.