Some say convertible doors will work. Just went through that on an '87 LX w/T-tops. I got some mint '90 convertible doors. After getting done painting and rewired so I could get the windows up, I realized it would take too much work to get them to fit. Would have to switch the glass with the T-top door glass (The vert door glasses are about 2" short when you put them all the way up) and you would have to cut the upper portion of the T-top doors off (where the mirrors mount up) and fit and weld them to the vert doors. Not worth the trouble in my opinion. Gotta find T-top doors or work with what you got. Going off different people saying "Oh yeah, vert doors will work". I never rewired and put them on the car till I was done painting. Big mistake.
I put 87 vert doors on my 86 T-top. Had to swap out the glass and the bracket the glass is mounted to and it works great. Just be sure the vert doors have the mirror up by the a pillar and not on the door is self. Check out my sig on the last page, I did a small write up on what I did.. Haven't got any pics though, but will try to get some of the bracket I am talking about.
Thats the problem I had,, I looked for 6 months before I found a set. When doing the swap it looked like a regular(hatchback) window and the t-top where the same, but I didn't have a regular to compare side-by-side. But the t-top and vert window are definatley different,, compared side bye side, the vert window is shorter. And that little bracket I was refering to is bigger to make up the difference. When I did the swap I just changed the glass;,, it worked but the window would stick up out the door about 1/2" to 3/4" when rolled all the way down. That's when I figured out I had to change the bracket along with the window after some investigating... I need to find that bracket and get some pics on my site....
Check out www.mustangttop.com Lots of good info there, and a forum to ask questions like this. There are several questions/answers already in there about this.
Yep....plus the moulding being different. If you have the 86 1/4 windows it will have a little mis-match on the trim by the glass, where it meets the 1/4 glass. I swapped mine out to newer 1/4 glass and that is one of the reasons I wanted newer doors....