I read your post all the way thru, without looking at the second link you gave. I got to the 7th page and started to think to myself, how would they have done the lathe when first made. It then occured to me that at the factory, they most probably just bolted a drilling head to the slideways (where the tailstock fitted) and then just drilled and reamed the head, most probably with some sort of manually turned drill.
Just the same sort of conclusions you came to from page 8 onwards.
I don't think the offset holes in the bearing shells is that important. The castings were most probably so badly twisted, the pre cast holes for the shells were just filled up solid with white metal and then drilled, they just turned out the way they did for no other reason. As long as the tailstock and leadscrew were in line with the spindle, that was all that would be required. The bearings would most probably then be hand scraped and clamped up to get everything corrected. Near enough was most probably good enough in those days.
You will notice, that a lot of lathes in this era had bolt down headstocks, most probably to allow the head to be put in a more central position before drilling. I did the same sort of fix on my old Myford ML2/3, but I actually fitted very finely turned bronze bushes, and repositioned and shimmed the head until everything was perfectly in line. My friend still uses that lathe in his small shop, and it still runs perfectly true after over 20 years.
If I was to do your old lathe, I would have gone the way of bronze bushes, just locked in with an anti rotation pin, then drilled or bored from the tailstock position.

The back bearing casting of the Myford also broke in roughly the same way as the other lathe you showed, and I got around that by machining the whole top half away, and bolted a new top piece on, made from steel. I never did paint it and cover it up, and if I get the chance, I will go down and take a picture for you to study, it just might solve that problem for you.

It is a real shame you live so far away, we could have had it machined up in no time.

John