Is there any interest in some castings

[Jonathan]

I'd want a bigger spindle bore (i'd like to be able to get 2" bar through).
For the spindle, I'd personally machine my own

Once again, same here.

One thing I'm wondering, why 3 castings?
Surely bed and headstock are the only castings that are really needed?

Perhaps tailstock or saddle? But as you say they don't have to be cast.

So roughly 24" bed length which I'm pretty sure is short enough to machine on a bridgeport. Is surface grinding strictly required since it's only to mount the profile rail, it's not a running surface? Just needs to be accurate...