Well, for anyone else who happens upon this, you don’t really need any changes to the post processor for lathes with toolholders on the operator’s side. The reason is the default way to setup your axis is for X+ to be toward the toolholder side (away from the spindle), in this case the operator side as well.
So when you draw in BobCad in the 90 to 180 deg quadrant, you are always drawing in the X+ side by default.
In order to visualize what the actual motion will look like, I’ve found if you look at it from ‘bottom’ view this will match the axis orientation and is what the motion will look like on your machine (when you look at it from the top). That makes X+ to right of spindle and Z+ away from spindle.