Agree with most if not all comments. That MG will go back inside without too much trouble. You will need some hardware that is somewhat specialized and some rubber isolating pads for the MG mount points. Some of that may still exist on the base plate where the MG resides now and in the worst case scenario something can be improvised. Feel free to reach out if you need details. I have lots of photos and what not. The 4x4 boxes Cal mentioned can go away as they were added for a junction box for the extensions wires that were added to move the MG out of the belly of the lathe.
My lathe is running the same rig / inline exciter / control panel / and most certainly a 230 VDC exciter.
I would definitely make sure the MG (main generator and exciter generator) brushes and commutators are all in good shape and tuned up before you cram it back in there.
Here is what it will look like tucked back in there (sans the VFD cable powering the MG motor)
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Sorry for the rotated pictures....still haven't figured out the picture posting thing here.