MY dyno and ET slip, What do they tell you?

Dustd - If the one you mentioned in the PM is what they say, I think it will help. It may not be perfect, but it should be a bit better than what you have. It may be a slightly lower stall than what the 440 had tho because you have a 6% longer stroke and probably more power. IMO, if you can get it for a super deal it's worth a shot. If you can't get a deep discount regardless of it's low miles, call and have one made for you. It's no savings if you have to buy a convertor twice.
Also, fix that tach. It's imperative you know what you're trapping at the stripe to calculate slippage, and to see in relation to the dyno's curve where you are rpm wise. It also helps with consistent launches, which will be the next thing to work on. IMO, no sense in wasting time tuning the suspension until the convertor issue is debugged.
If the results are correct (chassis dynos are notorious for being off) you're making plenty of steam. You just have to get it through the drvietrain and to the ground.