with 10in 3500 convertor ,12s with 3.55s isnt hard to do . 99.9 percent of performance engines want more convertor than what you have now. Keep in mind that a STOCK 440 magnum has a torque peak that occurs at 3200 rpm. I feel that the biggest thing holding you back enginewise may be the manifolds. A set of small headers(1 3/4 primary) will boost the power from the bottom to the top. I forgot what carb you have, but a 750dp works great on mild 440s.