70-71 Hemi springs. What differences?

I have two sets of original B body Hemi springs

2539793
2539963

and

2539794
2539964

What would make them different? They appear to be identical. I see them both listed for B bodies up to 71.

According to Frank Badalson, 963/793, 964/794, 965/795 are all the same, just different years.

1966 street hemi springs are unique for that year only. Don't know about 1967, but 1968 - 1971 should be the same.