Nope, you can't change the latch on the door, the inner works are completely different. You can add the 80-up striker to the 76-79 body. Look at part #6A to see what the 80 up striker looks like.
http://www.jeep4x4center.com/cj7/door-parts-seals.htm
The windshield is the same on all CJs from 76-86. Hardtops and soft tops should interchange as long as you get a top with all the hardware. There may be a slight difference in the factory hardware, as some of the soft tops were designed to be used with factory full hard doors.
Bob
tufcj