hmm i just checked astros site and they must have changed everything recently.
This must be what they used to called the super t5
http://www.astroperformance.com/product_info.php/manufacturers_id/29/products_id/209 rated for 550hp/425 tq for 1600 and then they also have the one that is rated for 650hp for 1900. You can get the gear kit for 1k to rebuild your stock t5. Other places to look @ trannies are hanlon and d&d performance.
When they talk about the 2.95 gear set that is the 1st gear. Other t5s are like a 3.35 1st i think.
If you want to swap in a tremec 3550 you need ds spacer, bellhousing, clutch fork, and a new yoke. The 3550 wont hold as much power (somewhere around 350 hp i think) as the tko 500/600 or if you went with the upgraded t5 from astro. If you can id just get the "a-five" from astro and stick that in. pry cheaper than swapping in a 3550 and it will hold more power. Just get in touch with astro they can help ya out. I think there is a rep over @ corral. I know some people have complained of vibrations after swapping trannies but i imagine if done right you can get rid of them but then again why risk having to chase vib problems when you could just stick in a stronger t5