All of the plans at http://www.my-garage-plans.com are available in CAD format. Just remember that you have to have the CAD software (which is usually very expensive) to make any changes to them. You can usually get a reproducible version of the plans a little cheaper and make the changes right...
It's a good idea to check with your local government building office to find out what their requirements are before starting a project of this size. Some of them will let you get away with a simple sketch, but some require plans stamped by a licensed architect. Also ask them how many copies they...
Zeke is right, that's one large span. The biggest gambrel roof garage plans I've seen measure 33' x 32'. I've posted a picture of the plans at http://www.car-garage-plans.com/
If you are looking for garage plans with oversized overhead doors for your boat take a look at these 2 car garage plans.
Unless you are looking for garage plans with living quarters, most of the plans you will find are pretty straight forward to build. Some garage plans come with step-by-step...