I used to have to do this frequently with my Cuda (before the TKO swap), and also with a 69 Valiant with a 3 on the tree that I owned in the 80's and 90's. They both had sloppy, worn out shifters, and you could move the shifter out of position without actually moving the levers on the transmission. If you weren't careful, the shifter would slip into neutral without moving the tranny out of the gear it was in. Once the shifter was 'out of position', it wouldn't go into any other gear, including the gear the tranny was in, and there was no way to get it working again without crawling underneath. To get going again, I would make sure the shifter was in neutral, determine what lever on the tranny was in gear, then move that lever into it's neutral position, get back in and drive away. But, make sure you have the emergency brake on or the wheels chocked if you're on any kind of slope so you don't start rolling when you pop it into neutral. As said, a crescent wrench works great to move the tranny levers. A few years before I did the TKO swap, I put a better (less sloppy) shifter in the Cuda, and never had a problem after that.