Well hate to crush your dreams but the Gxp have the same trans as every other year so chances are that will take a dump as well and you'll be replacing it also. Get a built trans in decrease the chance of it breaking and assuming you've been through 3 trans you probably need a driver mod and stop beating on the vehicle.

To put the motor/trans from a Gxp I hope your able to fabricate its not a easy venture and hope you have deep pockets.