Hello everyone. I believe I have a very similar issue.
It’s a 1973 dart sport 340 car, with a 1971 360 and a 727. The 727 may be numbers matching, 340 long gone.
the car had been drag races then sat in a field for 20 years. The old owner stated that the rebuilt tranny and 360(probably has less than 300 miles on it). Then the son lost interest. Anyways, my problem seems very similar to the original problem on this thread.
So the car starts and idles fine. Has a mow but nothing major(most likely plugs or something). But when you go to put it in any gear besides park, with foot on break, it dies. It’s strange because it seems like it does when you release the break instead of when changing gear but not sure. The other thing that isn’t right is the linkage for the tranny. The orange tick is positioned about 1/4 inch away from actual park.
I was originally suspecting torque converter along with flex plate, but if the Neutral safety switch fixes it, that would be great.
I have a new safety switch on the way, because you can start the car in reserve(which is a definite sign of bad NSS).
Any thoughts at all?