Hi everyone. I am going to be making a set of connecting rods for my snowmobile engine. I need a shorter center to center distance so off the shelf isn't possible. My question is: If I machine these from 4140 should I have them thru hardened and tempered, or should I make them from a material that can be case hardened? The bores need a hard surface because they act as races for the needle bearings. Any info./ advice would be appreciated.