I've only skimmed the 7 pages of this mess, but it appears that folks are talking in circles. To your point made above, if you are throwing parts at a build, then it would make sense for you to just throw whatever converter you have at it, because you really don't care about maximizing your combo (ET and speed). For those of us that DO care about having a fast car, get a converter tailored to your specific combo or you will be leaving a lot of ET/speed on the table....its that simple.
By the way, this was posted in the RACE forum; therefore, I would suggest a custom converter everytime....if you posted this in the non-race area it might be a different story.