You have a Getrag 5sp, designed in Germany bought by GM. I would recommend finding yourself a 4L80(TH400) and beef it up. You don't have to know much about automatics in order to rebuild one. Just use common sense and a clean work area. Talk to
www.sonnax.com for recommendations on what you can do and what tranny will hold up fine to your application. Check out
www.atsg.biz and look in the "bookstore" section to find a rebuild manual. You may find other sources of information at
www.atsg.biz that will be very helpful. -Chris