I went with the T-56 for my 56 Dodge 408 Stroker. I will run it with the EZ-EFI setup.
I did a lot of research and unless you can rebuild and upgrade a GM T-56 the brand new in the box Magnum T-56 for about $2800 or so is the way to go. (a GM core will be 800-1200, and you are looking at nnother 800+ for a good rebuild and upgrade).
Yes they are BIG but the effort will be worth it.
I also have a fairly comprehensive parts list with prices for what it will take to install one to a small block. I learned that I could buy a complete kit for only a few hundred more than I could cobble it together myself.