Machining Engine Rods

I have a question about machining engine rods.
Will be machining them out of 4340.
The process will be:
Machine all outside dimensions to spec.
Leave the pin bores 1 to 2 thou undersize.
Heat treat.
Finish hone the pin bores .

My question is. How do you keep the rod from twisting when they are heat treated?

How hard you plan on making them ? And why harden them ? Use pre-hard 4140 and machine it to size .