Originally Posted by Neil F.
The YJ windshield angle for the upper part of the doors is different from the TJ so they will not fit.
The angle of the windshield is different, that's true, but the angle at the back of the windshield is the same - the TJ windshield frame is thicker at the bottom than at the top, so the windshield slopes more, but at the jamb where the door seals, the angle is identical, and the angles of the front of both TJ and YJ upper doors (and full doors) are the same.
Here's a YJ full door on a TJ, the angle at the windshield is the same:
But that's not why YJ half door uppers won't fit, it's as wwch99tj said - the pins are in different locations.
If you search around you'll find posts (might be on other forums) where people have modified YJ uppers to have pins in the right places for TJ doors.
One other thing - some YJ uppers have angled upper corners in the back rather than the curves that are required for a TJ - this is because the YJ didn't have door surrounds to make the curves in the door openings for the soft top, so you'll want to start with round-cornered YJ uppers - ones made for half doors with a YJ hardtop, not ones made for a YJ soft top.