I was readin' some of the remarks here and was wondering what kind of transmission you were getting. Also wanted to say, I have a close friend restoring his LS6 1970 Chevelle to near new original except he had been racing it with an auto trans where it originally had a 4 speed, he sold the 4 speed a few years after buying it in favor of the auto for drag racing, that said, he's pretty good about researching stuff before he buys and has recently received a 4 speed built to m22 specs from a company called Auto Gear in New York. Its supposed to be even better than a m22 for quality of the gears and other parts in it. Just wanted to let you know about it in case you hadn't already heard of them. I'm a newbie and still learning at 66 years old so if I'm off base, just let me know.
http://www.autogear.net/