fwiw,you can run a 33/49 with the stock d5 no problem.i ran my ta-60 with the stock convertor for a while and the lag was minimal.i went with one of bruce's 9/11 lockup convertors(2800)and i've been happy with it.
it's been my experience that most lag/spoolup problems have been fuel related,usually running too rich.that'll make you a slug every time.
later,sean