Yup thats what i was planning on doing. But Wrong with the money you spend on the TA is more... lol i can get a fully built 850whp turbo'd T/A for $7,300 with the extra money i have i can finish suspension and buy torque thrust wheels, some street drags, just a whole bunch more than what i did with the grand prix. Also the WS6 can be picked up for about 14k with anywhere from 25-35k miles on it. now that is just sweet to me. The car would seriously outlast the grand prix any day of the week when it comes to the trans at the same power level.
to answer the trans question.
Dynotech/W-body store trans
Gm 1" chain 3.29 gearing
300m input shaft
output shaft
Hardened 4th clutch shaft
brand new clutches
shift kit
3250 stall
All of that cost me $3,400 or so... i have to look at my reciept. Also the warranty is still good on it! I was looking around $2,850 for the trans and i would probobly just take yours so its less of a hassle.(depending on milage)