keep the c6. i don't like AODs a bit.....and pulling a boat you probably won't use OD anyhow. It won't save you as much fuel as you think. Buy a book ($20) and rebuild the c6 your self. I got a haynes manual a couple years ago and did my first one having never seen the inside of a tranny, it's stilling going in my mud truck. C6's are easy to rebuild and don't require any overly special tools.