The reduced 1D/2D spectra from DEIMOS/MOSFIRE and 1D LRIS spectra are provided at the Keck Observatory Archive (KOA):
https://koa.ipac.caltech.edu/Datasets/C3R2/
Format is FITS tables with fields "FLUX", "LAMBDA", & "IVAR"
README file here.
Spectra are in a format compatible with the Specpro interactive software: specpro.caltech.edu