OK, just dug up a bunch of buildsheets that I have collected over the years from parts cars, etc...

IIRC- Plymouth only included the 15" wheel standard on 340 'Cudas for the early part of the 1970 model year, then the 14" became standard. The Hemi suspension was mandatory with axle package cars, but not with 3.23 rears...
I have a sheet for BS23H0B321856 with a SPD of 429 and it clearly lists rear springs as 043/043. Shows 3.23 with D91 sure grip. Car has the W23 Road Wheel option. Also lists- S13 suspension...