I have never seen anyone get our lights apart with heat, in the many years I have watched these conversions with interest. I did, however, see where a headlight was ruined because someone thought they could do it with heat.

I would be careful going that route, I am fairly certain they can only be cut. When someone has a good, steady hand and a fresh dremel blade, I have seen them come off pretty cleanly, a little black RTV and they are good again...