http://67-72chevytrucks.com/vboard/s...d.php?t=754926
http://67-72chevytrucks.com/vboard/s...d.php?t=677979
there are the two recent ones I remember. I always liked art morrison but have no personal experience with their frames.
one thing I will mention is beware of proprietary parts. its great if they make their own control arms and whatnot, not so great if they sell the only replacement parts.
also if you end up with a MII (nothing wrong with that) equipped chassis, make sure you tell them the desired ride height. MII can get huge camber from lowering or raising so its better to set it in the chassis in the right spot.