The color temperature of bulb changes with current (also the spectrum). For relative measurements it is not an issue (transmission, reflection) and with reducing the current to 90% you can extend the lifetime of bulb significantly.
If you want to use car bulbs, than do not use old bulbs from 70's - H1, H2 and H4. They have bigger tolerances for the filament position. Use the bulbs with more precisely defined filament like H7 - you can select from long life (thicker filament, lower color temperature) to blue vision (higher temperature filament, lower lifetime). For higher light flux you can use H9, but that are not too much common. Use current source to get stable values of light flux and temperature (this way the calibrated bulbs for headlamps are used). In your case I propose to use nominal current for 12V, since you will get better lifetime. Buy the bulbs from Osram, Philips, Toshiba etc., but this suppliers are leaving the market in these days. I will avoid using the bulbs for signal functions (P21W, W5W, W21W
For wavelength calibration use the gas discharge tubes as mentioned before, since the spectral lines are well defined. You can use even normal Hg bulb for the start, you will see the spectral lines going out from the white spectrum. Perfectly defined wavelength is 2nd harmonic of NdYAG 532nm - the green laser pointers. With some limitations you can use also laser diodes, but the wavelength is not so precisely defined and is temperature dependent (you can tune it with temperature).
White LEDs (or the color LEDs with luminophore) are the worst case. There are color bins (it can be that digikey does not distinguish them) - the color is measured with 1-25ms pulse, but the color changes with temperature and current, so you need to take preventive measures to get rid of these influences.