I have a 2003 Haulmark 24' trailer. I wouldn't consider anything smaller than 24' for hauling a B body.
You're gonna want to put some stuff in the trailer w/ the car and have some room for hooking straps up.

I also wouldn't want to pull one with a 1/2 ton truck either. The weight isn't as big of a deal as the wind resistance...as far as power goes. If you don't go very far or use it much, the 1/2 ton truck may be ok.
BIG difference in towing an enclosed versus an open trailer when it comes to power and MPG.