Well, I think this is the logical place for this. All you real machinists, if you must laugh, do it quietly to avoid harm to my tender feelings...
It better than I can do. I'm still too much of a wimp to do cast iron. The furnace can do it, it's me that can't.
Not safely. I really don't want a 5 pound chunk of cast iron suddenly reaching escape velocity in my vicinity. If I can figure out how to match the bottom with the bore I might just go with it as is. That internal void has me concerned, I don't want the wall to crack first time I try to use it. CI isn't terribly flexible.
Drilling is always tricky. It will follow the void's. This is where a one tooth boring bar helps alleviate deflection. It can be saved with a bronze sleeve, but... Both should be bored.
Oddduck, this is the line bore setup for the blower, and I also use it for the crankshaft and cam bores on the smallblock. OMM mentioned the single point boring bar. If you rig your two index surfaces parallel with the lathe axis and use the carriage to feed, the bore will be aligned with those two surfaces. The counterbores could also be done by turning the cutting tool and feeding from the tailstock.
ESC, that might be the ultimate solution. Hyperprecision isn't strictly necessary, the shaft is just going to be turned by hand, it just has to be parallel with the two reference surfaces. I'll have to make a new boring bar, the Gingery style one I made doesn't go between centers.
