[70CHEVYBB]

I have a 72 cab and the doors that were on the cab were wery rusty well beyond repair. First thought was to buy new doors but decided to find good used ones. Found new good doors so figured life would easy. The problem is the window fram does not fit the cab well at all. When the door is closed the rear gap is to big abd the window frame radius is almost hitti g the cab radius. The door frame gap at the top rear of window frame is good but at the front its better than 1/2 inch. Same problem on the front of door. Lower part of frame is perfect and at the top corner its huge. Any advice on a fix? I do have the original window frames a n d thought about switching them?