I'm thinking the 456/457 where designed for SB motors in the 1967 to 1976 A bodies, the 002/003 where designed for the original 1968 SS Hemi A bodies, they work very well in all the other A bodies with BB and Hemi motors, stick or automatic trannys
My 1971 Duster with a 400 block stroker motor with all the aluminum parts your using had 49 3/4 % weight on the rear tires and 50 1/4 % on the front tires with me in it, it weighed 3450 lbs with me in it ready to race with a Unlimited race weight lift off hood with a hemi scoop on it and a unlimited Fibreglas front bumper
I did slide the motor back one inch on the stock tranny mount to enhance weight distribution and I slid the rear end forward one inch as well as stretching the rear wheel wells five inches, three on the front side and two inches on the rear side
I didn't run leaf spring on that car( it had ladder bars with coil overs and a rear track bar) but I have raced a BB 440 powered 1969 Dart with the 002/003 springs clamped on the front half on both sides only on it and a pair of the old Imperial 50-50% long shocks, it would 60 Ft. in the low 1.50s with 3.91 gears and 10.5x29x15 inch bias ply slicks on 8.5 inch wide wheels in the rear, nothing wrong with those springs at all