A good dual plane intake would likely help the combo more than a single plane. An original Torker intake isn't as good as the newer Torker II. Your gear would probably be a 3.23 or 3.55 if it's a Mopar rear end. A 904 and converter will run about .15 faster in the quarter than a similarly set up 727 due to less rotating weight, so that was a good move. It's just not as strong/reliable, unless built/maintained well. Overall, carb and suspension tuning would help the most. More info, like cam specs and current suspension mods, if any, would help others identify problems and offer suggestions.
Hopefully it's not a lock-up 904. Limited performance/converter parts.
