You should have started it while it was still in the old body. These are slightly more complicated than the engines from 93' and back. You will need both the Cummins ECU and Dodge PCM with the CTM all connected via the correct wiring harnesses, as well as all the proper grounds for the harnesses, sensors and power will need to be hooked up as well.
You don't need the transmission to start it.
I would not try to start it on an engine stand, it is very likely to fall over or damage something. Unless you have a monster stand.
If the PCM and cummins ECU are not connected, it shouldn't start, both read sensor inputs and feed between eachother. I do not believe the Dodge PCM will run without proper input from the CTM, but i'm not 100% on that.
Good luck.