I am going to put a new fender on the drivers side of my 72 chevelle. the problem is that my fender I have now shifted on me. It seems like it shifted back toward the door. Now the door won't/can't open without hitting the door. I was just wondering how to put my new fender on and how to do it so it won't shift like the other. Also I need to know what new parts I will need.

There is no way a fender can "shift" that I know of without a little help from some force. Are you sure your car did not get bumped in the front end?
No matter.
This is what body shims are for.
Don't worry about where the old fender lines up.
There is an excellent chance that the same shims will not work for the replacement fender any way.
You will have to fit the new fender. This will take care of the door clearance problem.

Dave