I have not seen the NAG1 mentioned here. That 727 would be great but you are not going to realize the fuel economy with it that you would with the NAG1. This transmission has been said to handle 1000hp! Russell Drake at Sound german automotive .com has this transmission dialed in for programming. Ask Chris at Hotwire about this possibility. If you are resigned to modifying the tunnel , you might as well check into it at least. Sure works great in my GTX with the 5.7 and I am getting 18mpg with it!