Last I had one from both Award Wieners and Coke Corner, both stated 100% beef on the menu sign at both locations. I made a point to find out because I won't eat a mix.
Personally I hate the buns they use, though, and can't eat them anyways because of it. I haven't had one in months since I last braved trying one (from Coke Corner; been over a year since Award Wieners) to see if I could learn to tolerate the bun so they could have changed them recently for all I know. I'm now curious and will probably stop in to check next I visit.
I don't eat corndogs so I definitely can't speak to those.