Unless the extractor rod has a large barrel or mushroom knob on the end the simple solution is to use the orginal rod and center pin, just shorten close to correct length , then use a fine file to get just right. Then take the rod to a machinist and have him chuck it up in a small lathe and reknurl the tip. I have done it on 4" to 2 1/2" conversion and even fixed up the end of a rod some idjit had smeared up with pliers or something. If I wanted to shorten a rod with a mushroom end and keep the mushroom I would cut off the mushroom shorten the rod, drill the mushrom to fit the rod, then silver solder it on.