i have a 1999 grand prix 3.1 v6 that is wrecked in the back what cars can i putt that motor in

Gave you a list in your other question for 3100 applications. After 1999 the 3400 was used more and the 3100 was phased out. They can be found up to 2005. However they are a bit different than your motor. But. You can install your 3100 into any 3400 car (1996 through 2005) and it will run without flashing the computer. Keep in mind you will need to swap your injectors to the newer 3100 style on the 2000 and newer cars. All sensors are similar. Just watch for sending units for lights and gauges they are different. Keep the ones with the car and install on the other motor.

Having said that however, the real question is why would you bother? Have you ever swapped one of these motors? There's a huge amount of labor involved. Why not just buy a car that already runs? Just askin....

You can get cars with good bodies with powertrain issues for cheap. I'm sure the previous car was good to them and they would like to re-use the powertrain that they trust. Buying used you almost always know nothing about the car and it may be a lemon. This way you can get a good body and your trusted powertrain. If they have the right tools and an engine hoist it's an easy job. I can swap 3100 in 8 hours by myself takin it easy in a w. The j's and n's are faster.