All most everyone of my cars have had manual valvebodys both with and without transbrakes..... I have personally had C4's, Powerglides, Turbo 350's and I know other people that have used AOD's, Turbo 400's, and yes even 727 and 904 Torqueflites..... No one I know has ever had an issue with there trans because of a manual valvebody including myself.....

As far as I'm concerned your being dealt a major line of bullshit..... The reason most people use the manual's is because they have a more positive engagement in each gear which will do nothing be increase tranny clutch and band life.....

You just need to find someone who actually know what the fuck they are doing.....