OneCNCXR3 Lathe CAD/CAM had a function where you can simulate the machined part from a model of the stock rather than a standard billet.

This applies equally to a casting or forging or a part already machined in another process.

Here are some tips on using the lathe Rest function.
This function provides simulation for your machine to assist in the ability to prove the machining before it is run on the CNC machine.

Here are some tips for using the Lathe Groove function in OneCNCXR3. 
The OneCNCXR3 lathe grooving function has various styles and settings for grooving and this will be of assistance in using the function.