5.9 EFI Swap
I subscribed to this thread as I am thinking the same way.
From what I understand, the 98 Ram has an all electronic transmission requiring the OEM computer to run it. You'd be better off with years 93-95 that has both the overdrive and lock up converter that can be wired up to work properly.
As for the fuel injection control, I think you'll be using aftermarket like megasquirt.