Ignition Coil ?
... So you mean wthout the ballast the engine
will not start so good?
67Dart273 explained it perfectly. However, he didn't explain why Mopar later used ballasted coils (I think), which seems to have worked fine (if you can call any 85-95 car "fine"). If your battery does get low, it will make starting doubly hard.
Coil PN's and data can be confusing. I have one stamped "for use with electronic ignition" I recall taking off a 90's RAM Van w/ V-8. The low voltage side measured ~2.5 ohm (tricky to measure), so I assume internally ballasted. I have it on my 65 Newport, without a firewall ballast, using a Crane XR700 (optical) that needs a ballast (best I can tell from instructions).
In my 65 Dart, I connected IGN1 & IGN2 at the starter switch, and run just IGN1 thru the firewall in my new wiring. Since I have an XR700 on it (temporary), I needed a ballast for my original coil (<1 ohm), so wired one in-line beside it to make it a "ballasted coil". Don't drive the car enough to say much about starting, though it fires right up, even though the ballast isn't bypassed during cranking.
For those that use Pertronix ignition, the original Ignitor needs a ballast, whereas Ignitor II or III don't. Any ignition control that requires a ballast is older fashioned (no dwell time time control). Read KitCarlson's posts for much info. Johnny Dart always claims the Chrysler ECU is bullet-proof and problem free, but most people here carry a spare module in the glove-box, many report failures w/ photos of "black slime" leaking out the bottom. Seems much worse now that companies are putting whatever fakery inside the imported boxes.