Hello and welcome.
There are literally hundreds of experts on all aspects of our cars on this forum. You will undoubtedly get the right answers especially if you post pictures. We like pictures!
Use the search function. There are hundreds of thread about transmissions and, what I think your problem is, your shift coupler located under that plate on the floor in back. It has nylon bushings that break/disintegrate. There is a
pelicanite who has come up with an elegant solution to wobbly/loose shifters.
So, try searching for "shift coupler" and "coupler whisperer"and you will have hours of reading.
And post a picture of your 74! Or no one else will answer you!