We have no power at the coil after engine swap?

The first concern is the flex plate. If you reused the original one, you're okay. If you used one from the wrong year, the number of holes in the tone ring may be different. If they're different, the crankshaft position sensor will report the wrong series of pulses, then the Engine Computer won't turn on the automatic shutdown, (ASD) relay. That's the relay that sends 12 volts to the ignition coil pack, the injectors, and the fuel pump or pump relay.

The first thing to look at is that 12 volts at the coil pack. Back-probe the brown / white wire. A test light is preferred because most digital voltmeters don't respond fast enough. Have a helper turn the ignition switch to "run". The test light should turn on full brightness for one second, then turn off. You might hear the hum of the fuel pump at the same time. This tells us the ASD relay is being turned on and that circuit is working. You can do this test at any injector, also on the brown / white wire, or either smaller terminal on the back of the alternator.

Next, the test light must turn on again during engine rotation, either cranking or when running. For the majority of crank / no-starts, this is where you'll find the test light doesn't come back on. The Engine Computer is not turning the ASD relay back on because the signal pulses from the crankshaft position sensor or camshaft position sensor are missing or the number of pulses isn't correct.

If the flex plates are the same for both years, the next suspect is the crankshaft position sensor got damaged. It must be removed when separating the engine from the transmission. You'll need a scanner to tell if that sensor is working. The cam and crank sensors are listed with a "No" or "Present" during cranking on Chrysler's scanners, or a similar indication on aftermarket scanners. You're looking for the one that doesn't switch to "Present" when cranking the engine.

You can also read the diagnostic fault codes to see if one is set related to either of those sensors. On older models Chrysler made doing that yourself much easier than any other manufacturer. Cycle the ignition switch from "off" to "run" three times within five seconds without cranking the engine, leave it in "run", then read the code numbers in the odometer display. That test went away on newer models but I don't know on which years it still worked. If it doesn't work for you, you'll need a scanner or a code reader. Be aware it takes some time for the computer to detect a problem with those two sensors, so it may not set a code right away. For that reason, do not assume they're both working just because no code is set. This is where you need the scanner to view the state of each one during cranking.

Don't concern yourself with the EATX relay. That is for the Automatic Transmission Computer. We never bother with testing relays. The simplest test is to see if 12 volts is getting to one of the contacts, then if that 12 volts is getting switched to the circuit under test. That's what you're doing with the test light at the ignition coil pack. If the test light turns on, you know 12 volts is getting from the fuse to the relay, from the relay to the circuit, the relay's contacts are good, and the computer has control of that relay. No other testing is needed.

Let me know what you find, then we'll figure out where to go next.