73 Duster build named Fred

Going from a 8 inch 5760 converter to a 9 inch 5200 stall slowed my duster approximately.25 in the 1/8 with a powerglide. My son picked up .40-.60 in the 1/4 going from a 4600 stall to a 5600 stall. These engines love high stall converters.
Was the 5600 stall the one I got from you when I bought the trans/converter from you?