truchevy is right. no shop is going to want to warranty a job like that and no customer is going to be satisfied with leaking t-tops when the shop is charging somewhere in the ballpark of 2k. its just not a situation theyre willing to walk into. like its been said before even oem ttops leak...what makes you think aftermarket conversion isnt going to. That is something you cant explain to someone that just shelled out 2k for a car. Ive worked at dealers before. Ive also seen people buy open air vehicles (ttop-vert-moonroof-targa-removable)
and rework a deal with the dealer for hardtops because they cant deal with the fact that in reality id say 75 percent of OAV will develop some type of leak.

Considering that I searched long and hard for a hardtop car and drove 1800 miles just to get one, you know my view on this topic.

My buddy is in school getting his master in electrical engineering. He has always love messing with cars and is currently working on a 98 mustang hardtop.
He is about 80 percent complete with the ttop conversion and custom body fabricating.
Im talking to him about doing a targa top coversion on my thirdgen. If you have enough money and free time you will find someone who is willing to tackle a ttop coversion. Just dont expect a warranty.

I'm not saying this to put down whatever skills your friend has when it comes to working on cars, but converting a 3rd gen hardtop to T-tops is hard enough. Going to a Targa top will require so much additional work (and weight) to stiffen up the chassis of the car that it really isn't worth it.

The 4th gen conversion is easy since all hardtops and t-tops were built with the T-top structure already in place - hardtop 3rd gens on the other hand, do not.

- Justin

yeah truchevy is right...the z28 i own is a hardtop and there is a 'bone' going through the middle of my roof where the t structure is. ill get pics tomorrow.