[Mr70]

Funny you bring this up,as I was researching this subject this week.
I found it depended on a compilation of the weight of options ordered.

For 1969 & 1970 L-34 & L-78 Novas with Std.Suspension.
They used Ft. Coil spring:
*3955720-YF if 0-50lbs.
*3925814-EY if 51-132lbs.
*3955721-YH if 133-214lbs.
*3955722-YM if 215-296lbs.
*3955723-YP if over 296lbs.

If HD Suspension ordered.
They used Frt. Coil Spring:
*3955727-HH if 0-294lbs.
*3955728-HJ if over 294lbs.