Transmission issue

[Jmageee902004]

My 1964 chevy 3/4ton 4speed transmission is having problems shifting. It shifts fine when the truck isnt running, but seems like it isnt disengaging. I press in the clutch and it doenst allow me to shift into or out of any gear. I was told this could be a stuck clutch plate, but cant figure out how to get it unstuck.
What happened was about a month ago i get in my truck after it sitting for a few weeks and back it out of the drive way. when i go to shift out of reverse and into first, it wouldnt go into first or any of the other gears. So i turned the truck off put it in first and started it up while already in gear.
Some more information, i adjusted the clutch rod and what that did was when i had the truck running and driving around the block in 2nd i was then able to shift out of second (i couldnt shift out of second easily or everytime) but not back into any of the gears.
Any help or insights would be much appreciated, i also hear maybe broken clutch forks? but dont know how to check for that or even check for a stuck clutch plate.