DC unregulated power supply
For a 70 V DC supply with a capacitor filter, the AC RMS voltage should be about 52 volts. If you use a 48 volt transformer, that would provide about 65 volts allowing for voltage drop in the 3-phase bridge. It is certainly possible to wind a transformer for the voltage that you need.
Rather than power factor correction, you might want to consider harmonic current reduction. Harmonic currents cause reduction in power factor, but the correction method is different.