1970 C10 Suburban Trans Issue

[Tilldogg]

Question, Driving home yesterday my burb was juddering as i take off and then would not shift into 3rd, then it would not find reverse and no matter where the column shifter is it pulls forward only,
anyone had this before? why does it only go forward if in reverse? is the linkage messed up or internal issue - i was in traffic it was struggling to pull away, like it was pulling a big load,
I have noticed over the last month the shifter when it says D it isnt in D i have to move it to like 2 none of the shifter things line up anymore, so Park is like half an inch off the P , and R isnt where R is on the column more where P is,

I am at a loss here as i do not know much about transmissions and i am in England and no one here knows them, so i have to ask for help,