The 6466 is a legitimate 9 second turbo with matching mods and tuning. With it only being available in a DBB version, I passed on it. The cost was prohibitive. There was little track data for me to go on as well, as most haven't got the balls to max a turbo out.
Jack's been a Turbonetics dealer for years, and knows his shit. The 6468 is likely in the same ballpark as the 6466. Turbonetics turbos, from the reading I did on them years ago weren't a true DBB. One side was a BB...and the other was journal. As to their durability, if Jack is still selling them, then that should be a hint.