I dont have a T56 in my Z but I plan to at some point. For me the benefits of this transmission are that it is extremely durable and the most beneficial aspect is that it has a overdrive ratio of .5 in top gear which allows you to run steep gears in the rear end while still being able to drive it on the highway. I have a 350 Z which has a TH350 trans in it with 3:55's in the rear end and it really sucks to drive on the highway because the engine is turning so fast. If I was going to the trouble of putting a manual in my Z I wouldn't use anything but the T56. I'm not positive but I believe that this trans is pretty large so it might me a little tough getting it to fit but I know that it has been done without to much trouble.
I would also like to thank you for your respone to my question about cleaning up and painting my engine compartment. I think I have decided to just leave the big holes there and cover them with rubber plugs. I will probably use bondo on the small holes and hope for the best. I'm glad I can use enamel on the body. I think it will look really good in the body color.
Have a nice day