How much is fuel where you are? Are you building a driver? Do you ever plan to sell? The 6 cyl is original, fill it up with oil and store it. It may be hard to overlook the LS1 with an o/d trans. 400 hp+ and easily 20mpg. This is hard to pass up. While I understand wanting to keep it all Pontiac, I have a hard time with beating your numbers matching motor to death. I don't have an LS1 in mine, but my original is full of oil in a large bag. I am sure most of us can't wait to find that open stretch of road to nail the snot out of it. I know the first day the weather breaks here my right foot will be on the floor! I don't think I would drive & enjoy it as much with the original motor. I did about 4000 miles this summer at 10mpg.