Profile Drop Down On Registration

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I need a profile drop down on registration that says:

* Model
* Photographer
* Stylist

I know you can do this via profile field manager, BUT I need:

Depending on which one you select depends what your custom user title is..

So if you are model, your usertitle is model,
photographer - photographer
stylist - stylist.

Ideally, it would put them into that usergroup too.

How do I do this?