I have so many Motrons, it's not funny. Those shocks are sooo cheap. The bottom/insides of the shocks are plastic. I've replaced a few of them because they crack and break where they connect to the swing arm. If you try to twist the bottom off, they will probably break. I certainly wouldn't try heat, either. Since Motron isn't that popular a brand, used shocks are tough to find on ebay.
You are probably better off getting a new pair that fit. They are 280mm long with 10mm bolt holes. And since this is going on a trike, you might want something a little tougher. (edited)