Yes they are....I meant by the GT having something special engine wise....by maybe a different cam or something? but I don't think there was much different.
I know alot of the base model grand ams and the GT in 99 (start of the new body style) had the 3.4l v6 and later in production they started using the 3.8l v6 in more of them.
so first check to see if the donar car is a 3.4l or a 3.8l or if its a 4 cylinder for that matter.
I am not sure what if any issues there would be going from a 3.4l to a 3.8l or vise versa but no matter what you do....you have the car the parts came off of to make it work so it would just be a matter of swapping out parts!.