You would need a computer for a manual trans car so it doesnt care about the electronic controls for the transmission.
yes, you can cut a notch in the bellhousing and there were indeed 727 transmissions in early 90s vans with the efi magnum so there is a factory flexplate that will work for that application. I want to say one from a 92-94 van maybe? It would be wise to see if you could find one in a junkyard somewhere and look at what it has. I do know though for sure that the vans used a magnum with a 727 even if for a short time.
The location of the crank sensor is very important, but since it's actually bolted to the block you would only have to make sure the slot cut into the bellhousing is where it needs to be.
If you found one of the 727 cases that was originally set up this way you would be ahead of the game. Heck you could take the computer and everything and just swap it all in as is.
The efi magnum engine in a dart would be a lot of fun since the magnum has real good low end torque. It would be perfect for a fun driver, and with those SCT tune things, you could do some nice changes to the cam and heads too for even more power while retaining the factory efi too.
I am sure there are other people with more info for you. I'm only trying to kickstart this since I see no one has replied. Good luck!