1972 dart - stopped running while at 50 mph ? no warning

these from earlier today and really early today


slight update . before going to the auto parts store to get the spark tester and alligator leads , i thought i should check a few things in case i need parts . just adding it here in case it points to something . i tested the condenser ( i think ) with a test light between the coil to dist. wire contact and its location on the coil , with key ON . i did not light up . meaning probably good according to something online . not 100% but if it did light up , it would mean a problem with it . "cleaned" the dist. wire and condenser contacts under the cap and the condenser body and its clamp with 320 sandpaper . tested the dist to coil wire for resistance . it was not getting a steady reading before cleaning the contacts with 320 , after it read a solid 0.2 - 0.3 ohms on the multimeter . not sure what it should be . ( later on i remembered the grommet for that wire on the dist. housing was kinda worn out . so maybe the wire is touching the housing . not sure if that would be enough to cause this condition . but i will look at it again later . ) i reset the points gap , and actually got a dwell reading this time . near 20 to 25 i think which i thought was close enough for now . after all these i hit the carb with a shot of starting fluid and still nothing . no start . then pumped the gas and tried in park and then again in neutral . still zero . next tested resistance of the coil to cap wire , but could not get a steady reading . it would just flash a number briefly before going back to 1 , but flashed anywhere from 565 to 998 . so i got the 74 valiant slant six started up , and after a short warming . took out its coil wire and put the darts in there . the valiant ran , seemingly just fine . i did not try the valiants coil wire in the dart , because i don't want that to get screwed up by whatevers going on with the dart . just paranoid probably , but not doing that . i checked the resistance of the ballast and got a reading of 1.7 and 1.8 , but , again , not sure what that is supposed to be . also , i grabbed the rotor and tried to turn it to check for play . did not move in one direction , did move a little/some the other way , and slowly returned a bit . not sure how fast it should spring back , but the dist. is old/original . i looked for a ground strap behind the motor , looking for one going to the firewall , but did not see any . however i did see this wire that looks really questionable down where it touches the trans ? where its been getting coated with oil and dirt for 50 years . what is that ? is it something with the neutral safety switch ? ( black wire , right of center , both photos ) thanks again , everyone .


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ok , so i tried to check the timing , with a remote starter switch , but could not get the timing light to flash much at all , one or two random flashes , and nothing . tried two different timing lights a few times each , same result or nothing . i feel like i am doing something wrong . so i could not find a solid core wire , so i used what i have . i tried to check spark at first with the remote starter . zero from coil or plug wire number 1 . then i re read what you said a few times ( i takes me awhile ) and tried with the key . from what i could see looked like an ok to good spark , had the gap at about 3/8" , from looking between the bottom of the hood and cowl and with sun in the mix . heard a zap zap sparky sounds too . tried the same thing by putting the wire with tester in the cap where number 1 goes . got nothing , no spark , no happy sounds . then pulled the cap , pressed the remote starter , rotor is spinning , points are opening and closing , but no sparky goodness from those either .