Work on enough A-Bodies, and sooner or later you'll run across a broken doorjamb at the striker pin. Why is it that this problem seems to crop up in A-Bodies more than on other Mopars? The way the striker pin is attached is different than it is on later B- and E-Body cars. In both cases, the hole in the jamb is backed up by a floating captive plate that the striker pin screws into. The difference is that later B- and all E-Bodies have a serious chunk of metal that the plate is attached to, while on As, the floating plate is simply hung on the jamb's thin sheetmetal. One thing is for sure, there's only two types of A-Bodies, those with broken strikers and those that are going to break.
When I purchased my '70 Dart 340 project car, sure enough, the striker was busted. On this car, the pin was already solidly (and roughly) arc welded to the jamb and backing plate, defeating the stock provision for adjustability. This was the car that got me hip to the problem. Cruising the salvage yards for A-Body pieces, I began noticing the same condition-door jambs either cracked or shored-up with hacked repairs. At least my clean daily-driver '69 Dart's jamb was intact. Purchased several years back as a low-mileage original, this thing was as solid as they get. Driving down the freeway a few months back I heard an uncharacteristic rattling vibration over my shoulder, either from the door or quarter. A quick open and shut of the door, and it was still there.
Closer inspection revealed that the once-solid striker was now wobbly. Blighted. Thirty years of catching the door worked the metal under the striker pin's large washer to fatigue. Finally it broke loose like a coat hanger bent back and forth. At this point there was nothing to do but pull out the tools and fix it. A broken doorjamb isn't a cosmetic ding that can be puttied and painted, it's structural. Think about it. If even the factory metal eventually gave up, anything but a top-rate repair hasn't a chance of surviving. There are ways to reinforce the mechanics of it, adding an extra layer of sheetmetal, or a larger diameter washer under the striker pin-but none of these mods look stock. Rather than re-engineer it, we repaired it back to original condition, and hoped it lasts another 30 years.