Check out the section on the protein myth and body building.
Note that the 9th and 10th editions of this standard reference for RDs became hostile to veg*nism after Krause died after the 8th edition was published. So, you won't be getting any pro-veg slanted propaganda in this book. The new editors are completely comfortable with the disease-promoting Standard American Diet.
I don't know about BIG muscles, but they are pretty toned. It's tough, at first, to become a vegan bodybuilder, but once you get used to your body and how it reacts it becomes pretty routine to put on and then maintain quality (non-flesh fed) muscle.
Typically, I'll take some of the best bodybuilder's diets and modify them until they're vegan. I spent a lot of time on veganbodybuilding.org and started looking at several other sites until I had a regimen that worked for me.
Remember to eat at least every 3 hours and get sufficient rest!