Go to your local feed store and ask. They should be able to steer you in the right direction. Look for the ones with 11-14% crude protein. The higher it is, the more energy they will have. As far as helping get his muscle up, I don't know if the protein will help, but lots of exercised will. :) Hope I helped a little.
I actually have to travel a few towns over to find Triple Crown, but it's worth it for my girl.
Ok...off topic comment to Peggy Sue (sorry MIE ). I saw on another forum you found the company that owns Buckeye and were marvelling at the other people/pet brands they own. I happen to work for that company!
But unfortunately, I'd have to travel really far to find Buckeye (at least the last time I checked).