The best I have heard about since I posted the original comment is the GM 700 turbo auto box which has a 4th ( overdrive ). Using that ( still checking that it will fit ) with a high performance torque converter would improve hings especially because 1st is a much lower gear. I have been put off going full manual because of the cost / complexity. But the 6 speed you mention sounds much more interesting, perhaps there is a way after all ? Do you have any leads to find out more ?