Boxing to Kickboxing

I was wondering what habits does a boxer looking to transition to kickboxing, and vice versa, need to change? What habits built up over the years are beneficial, and which ones will get him into trouble?

a wide stance is bad and an overrelance on lateral movement in close can be trouble, especially if you are moving to the guy's right just outside of punching range.

Some people say head movement can be trouble in Thai, but only if you are a Pernell Wittaker type (go very low with the bobbing and weaving) personally I think it is to advantage. Most other habits of a good boxer will transition well to kickboxing once leg kicks and defense are addressed.

Does the stance change much? Do you find that you
need to square up more to free both legs for kicking?

You might have to 'square up' a little bit more.

Also too much weight on the front leg = good target for the round kick.(Perhaps a 'less wide' stance)

Be lighter on your feet. Less bobbing and weaving. Weight on your legs are easy kicking targets.