Marinepower has them http://www.marinepowerusa.com/Products/60L.aspx
PCM has them http://pcmengines.com/engines_zr.php
Raylar has them http://www.raylarengine.com/550_engine.html
exhaust for LS marine engine:
In fact the only player that is behind the times is Mercruiser.
While your idea has merit without a good source of income
your not gonna get far. To restore any boat well enough and different enough to have people take notice of your work would mean spending a lot of cash and will take a lot of hours.
Kinda hard to make that cash if your going to school and spending all those hours restoring a boat and hard to spend those hours restoring while your going to school and making cash . Its a Catch 22. Way to do it is take a good job like the one offered to you by Whaler after you get your degree and restore in your spare time.
That way you get degree+money and headstart on your dreams all in one.