I know convertibles had heavier rate rear springs because of the additional weight & I thought A/C had something to do with rear springs also but I guess not. EDIT - I added a few, thought I had some convertibles (somewhere?).
Axle packages "upped" the springs on 340/383 cars.
Went thru a bunch of b'cast sheets:

JH23C - 013/013
JH23C - S13 - 042/042
JH23G - 014/014
JH27G - 015/015
JH23H - S13 - 043/043
JH27H - S13 - 044/044
JH23J - S13 - 048/048
JH23L - S13 - 043/043
JH23N - S15 - 034/024
JS23N - S13 - 043/043
JS23N - S15 - 034/024
JS27N - S13 - 044/044
JS29N - S13 - 043/043
JS23U - S15 - 034/024
JS23U - A36 - S15 - 034/024
JS23V - S15 - 034/024
JS23V - A32 - S15 - 034/024
JS23V - A33 - S15 - 034/024
JS23V - A34 - S15 - 034/024
JS29V - A36 - S15 - 034/024
JS23R - S15 - 034/024
JS23R - A32 - S15 - 034/024
JS23R - A33 - S15 - 034/024
JS23R - A34 - S15 - 034/024
JS27R - A34 - S15 - 034/024

BH23B - 013/013
BH23G - 014/014
BP23G - 014/014
BH27G - 015/015
BS23H - S13 - 043/043
BS23H - A31 - S15 - 034/024
BS27H - S13 - 044/044
BS23J - S13 - 048/048
BS23N - S13 - 043/043
BS23U - S15 - 034/024
BS23U - A36 - S15 - 034/024
BS23V - A32 - S15 - 034/024
BS23V - A34 - S15 - 034/024
BS23R - A33 - S15 - 034/024
BS23R - A34 - S15 - 034/024