Follow-up spectra and evolutionary models obtained for the manuscript "A hot subdwarf–white dwarf super-Chandrasekhar candidate supernova Ia progenitor", published in Nature Astronomy (https://doi.org/10.1038/s41550-021-01413-0). This repository includes: Spectra taken with the Double-Beam Spectrograph at the Palomar 200-inch telescope, reduced with a PyRAF-based pipeline (https://github.com/ebellm/pyraf-dbsp). Files start with DBSP*, and are separated by spectrograph arm (blue or red). Flux (flux.spec) and flux error (flux.err) are in different files. We provide both fits and ascii files. Spectra taken with the Echellette Spectrograph and Imager (ESI) at the Keck II telescope, reduced with the MAKEE pipeline (http://www.astro.caltech.edu/~tb/ipac_staff/tab/makee). Fits and ascii files are provided. MESA inlists and resulting data for simulations carried out for the paper. A README file is included in the zip file with further information.