Anybody ever cut the T-top roof off a donor car and weld it on to a hardtop car?  Any thoughts and opinions on this matter are welcome.  

What year and model? If it is a second generation Firebird/TA, use the donor car as a template and cut the openings and use all the t-top hardware. I saw a car once that had a transplanted roof, it wasn't done very professionally, leaked like a sieve and had lots of bondo at the joints, and probably wasn't very safe to boot.
Steve  

A 79 TA would be receiving the T-tops.  I talked to Clayton Custom Cars out here in NC and they said they would cut it off at the seams just below the roof on the b-pillar and weld the entire T-top roof on at the seams.  I think they mentioned something about doing a little overlap as well.  Is there any structural difference between the 2 roofs?  

I've been researching the t-top swap myself, since I always wanted some. I just bought a donor t-top roof and panels from another 79 for one of my 79's.

Your custom car shop is correct about replacing the whole roof for your 79.

I would brace the inside of the car before removing your roof to maintain your dimensions. This means removing the interior to be able to tack weld some metal tube bracing in temporarily.

You want to use the factory Fisher t-top roof from a donor car, a 78 to 81. There are factory seams at the rear where the old roof would be removed and where the new roof would be welded back in the factory position.

The front posts require more study. When you get a t-top roof, get the front pillars cut below the bottom of the posts, so you have plenty of metal to work with. There are several layers of metal layered in the pillars. So far, it looks to me like the best way to put them in is to remove the lower section of the outer skin on the pillars, which makes it easier to graft the inner structure to your original inner structure for a strong weld. Measure from various reference points to be sure the dimensions are right before welding. Trial fitting the old windshield would be a good way to check the fit while doing the work.

You could go to www.transamcountry.com and do a search of the forums for roof swaps or just ask your question there for advice. I've also been doing a Google search for roof swapping and found some info at www.nastyz28.com , a camaro site.  

Also, here's a very good thread I found at transamcountry.com . http://transamcountry.com/community/index.php?topic=401.0

As for the structure of a t-top roof versus a hardtop roof, everyone will tell you the hardtop is stronger for obvious reasons. A Fisher t-top roof being a factory roof is certainly strong enough for normal use. For higher performance use, it is recommended to install sub-frame connectors under the car to add rigidity.  

go to classicresto.com, look under past projects and then for the 77 Formula. They did a Fisher T-Top conversion that looked awesome. I am sure you could call them for advice also.  

been wondering lately the feasability of t-tops on a 1st-gen. i know it would be alot of work, not to mention a little crazy. has anyone else had pipe dreams like this?  

abything can be put into anything. the key is the right approach and engineering to the project.  

The current issue of HPP has an article about the 76 50th anniversary TA and shows how the Hurst Hatch t-tops were instaled. The original hardtop roof was cut and a brace panel was riveted in to help reinforce the roof. If you have access to a donor car, I would compare the two roofs with the weatherstrip and headliners removed and consult with a good body man. It's been years since I looked at one, but I suspect you'll find that even the Fisher t-tops are just a factory brace kit that can possibly be removed and welded into your roof, that way you aren't compromising the strength of the roof. If you intend to put any power thru this car, I would stay away from t-tops, especially a roof transplant, even with subframe connectors. The next time I'm at my buddy's wrecking yard, I'll try to get some pics of a 79 TA t-top he has for reference.
Steve