Boxford A4/A3 HSR mill restoration

I've been given a Boxford A4 HSR. I don't have a manual so I don't know how original it is. All I know is that an Arduino gerbl (gerber interpreter / controller) has been put in. It currently has a bosch GSS 27 110V 500W die grinder as a spindle with a speed of 27'000 rpm. I don't know how appropriate this is and if it can fit different mill bit / collet sizes or if I should change this.

The motors are HY200-2240-0290-ADM8, I don't know if they are original I expect so. I can't find a datasheet for the precise model but I can as far as HY200-2240-0290, Hybrid stepper motors 200 steps, 2.2" diameter, 4" long, 2.9A. The data sheets also say to run on 75V. The transformer is 20V, yes it's an actual transformer, rectifier and smoothing capacitor so peak voltage of about 28V I guess. The stepper drivers seem to be generic ones rated to 40V. So I suspect not original.

Should I change the power supply and drivers for 75V ? I'd like to mill aluminium.

Any advice welcome.