I got a Lucas Sports coil from TRF at the 2009 Triumphest, that lasted less than a year. Not fun, especially since it died while I was on the freeway in rush hour traffic on my way to a TR club meeting. I grabbed a 1.5 ohm Pertronix coil that I had on hand (for a Stag) and used that with an external ballast resistor for several years. That worked fine, but I eventually bought a 3 ohm Pertronix coil which is what's on there now, just to clean up the temporary resistor installation. (It also works fine, so far at least.)
If you have an original type coil wire, you'll need to change it to a plug-in type terminal for the Pertronix, instead of the original screw-in. Easy enough to do, just cut off the original tip of the wire (saving the brass washer that is soldered to the wire), and remove the nut. Any parts store can sell you a clip & boot to fit the new coil (if they didn't come with it). Slide the boot on, then strip roughly 1/8" of the insulation, fold the center conductor over and install the clip.
The Pertronix already had screw terminals for the low tension connections, so just undo the nuts, remove the quick connects and drop the ring terminals into place.
It's also slightly smaller diameter than the original, so I used a section of aluminum beer can as a spacer. The thin aluminum cut easily with my pocket knife, so that was trivial.
Don't be too surprised if 3 ohm coils are hard to find in the local stores. I didn't bother looking this time, but years ago I checked several places and no one had them. Practically all American cars used external ballast resistors and 1.5 ohm coils. Also be careful about the "12 volt" designation, as some 1.5 ohm coils are marked "12 volt, ballast required". You can certainly use one of them, but you'll want to be sure to supply the ballast it needs (otherwise the points will burn up in just a few hundred miles BTDT). The store should have the ballast, but they may not know what it is. If not, ask for the ballast resistor for a 66 Dodge Dart with a 225 slant six