Starting Problems, HELP!

Okay, before you say Ballast Resistor or Ignition Cylinder, :naughty: read my post first! I've got a 1967 Dodge A100 Van with a 225 Slant 6 & 727 Trans. To start off from the beginning, I just did an engine swap on the van and the van ran perfectly fine before the swap. Reason for the engine swap was, it needed a valve job and I found a newly rebuilt one for cheap. So I swap the engine put everything back where its supposed to go. Started the engine, tweaked the timing and it starts right up and idles good. I started it everyday while still working on other stuff (brakes, etc.). So, one day I go out and start it up and I turn the key, it starts but when I let go of the key engine dies "fast". If I leave the key turned all the way it will run smoothly but starter is still engaged. Carburetor is getting gas too. First off, the person who owned this van before me did a bunch of modifications to it with later parts. :confused: Its got an ignition module from a 72 Dart, which didn't come in the 67 vans and a voltage regulator also out of a 72 Dart. And other silly mods, which were just silly!
So first off, I did my research and I replaced the ignition cylinder and no luck! Then I bought a ballast resistor for a 72 Dart, and no luck! Then I bought the ignition module for the 72 Dart, and no luck! Keep in mind that all these 72 Dart parts are exactly the same as the old parts that are being replaced and the van ran fine before hand. Then I bought a new starter relay and no luck! Took the starter off and had it checked out and it was good. I also replace the voltage regulator, just because, and no luck! Checked all the wiring for fried wires or bad connections and they all looked good! :doh:
So, I'm stuck and don't know what to do! I'm kind thinking its the ignition. I don't have an volt meter, but I can buy one if needed!
Any suggestions?