If you actually are doing 'daily 10-mile runs' then I think you'll be losing muscle mass, certainly from on top. Not a bad thing from my POV, but probably is for you if you want to take part in a bodybuilding competition.
But you'll be building/maintaining your cardiovascular system very well, so in general fitness terms as opposed to looks, fantastic

.
I do hope you don't do any 'artifical enhancement' for your bodybuilding, but none of my business and entirely a matter for you.
In terms of nutrition I'm sure you know the drill: plenty of fresh fruit and veg, plenty of fluids, plenty of protein for muscle repair/maintenance, and just enough carbs to fuel your training and maintain energy levels.
In terms of supplements, especially for proteins, I use these guys:
External Link/Members Only. Once you get a few regular orders under your belt you get sent regular discount emails with anywhere from 40-60%-off.