I haven't run these mini lathes, only the Sherline, Prazi and
Craftsman, so I don't really know what the ways look like and gave only
a general approach to fitting a plate to them. The milling attachment I
made for my 6" Craftsman lathe fitted onto the saddle dovetail but it
was done on a Bridgeport.

The usual way to bore offset holes on a lathe is to clamp the part to
the faceplate using some sort of alignment fixture, or center punch
marks placed by geometric layout techniques. Are the wheels are too
large for this?

You could attach a slotted angle plate to the base I suggested and use
the lathe like a drill press, although a real drill press is better.
The base could be held down at the edges the same way the saddle is.

The obvious answer is to buy a mini mill. See how much trouble milling
on a lathe can be?

jw