Re: 4l80e or t56?
Given the OP's stated wants i think he clearly made the correct choice. That does not however mean that T56 would be best for everyone. (and that is why i voted T56 back when he posted this)
I have a 4l80 in my swap and have been happy with it. If the cost had been the same I probably would have gone T56 but it would have taken ~2k more in addition to the added complexity of the swap.