I tried modeling clay and could not get it to work right. Years ago I carved a spinnerbait head out of wood, cleared it then made a 2 piece silicone mold. That mold I used to pour some Alumilite resin in because it would handle vulcanization. Never had a lead head made because I decided on something else.
This winter I will be making a spinnerbait head from a small JDM crankbait as the base for the body. Busy trying to learn spincasting right now so I don't have time to mess with it.
Allen