right now I have yj half doors on my cj7.
I need to run tj/lj uppers.
I know that in order to do this I will have to modify the tj upper to work with the yj lower.
so Im thinking that I might as well get rid of the yj half doors and just run tj lower and upper half doors.

Will TJ/LJ lower doors fit on my cj7

:)

The latch is at a different type and height so you'd have to figure out how to install a TJ-style "loop" striker to replace the CJ pin striker, and you'd have to figure out how to mount it at a different height also.

You also may have trouble getting the doors to close or seal properly, the weather strip and door jamb profiles are different between CJ/YJ and TJ's, but some people say they have been successful with this.