in my opinion, the 4.10 gears have just as negative effect as the converter. mushy converter plus low axle gears reduces the drum rpm and acceleration rate. I don't think that engine needs either of these two factors. a lot of cubes and small cam should be a torque monster. I have a simplistic philosophy about some of this; you can let the engine do the work or you can work the engine. I think in this case the lower gears and looser converter are working the engine instead of letting it work. this engine probably makes gobs of low and mid-range torque and probably could be tuned to work with a stock 11 3/4" converter. add a 3.23 or 3.55 gear and I bet results will be different.