More and more shops are doing the late Gen 3 Hemi into all kinds of old Mopar cars and trucks, yours would be a perfect choice for one As far as power and economy you already know that the right foot determines the fuel mileage, right Do you know the true weight of the 09 Challenger? If so and if it is above 3800 lbs the Cuda should get the same or better mileage than the heavier, less aerodynamic 09 I raced a 1970 Hemi Cuda 4 speed car in the mid 1970s for several years in NHRA stock, it had to weigh 3420 minimum without the driver back then, it had a set fo Crager steel SS wheels and it had to have at least a 1/2 tank of gas to make the minimum weight I'm almost positive the Gen 3 Hemis are way lighter in weight than the original all iron 426 street Hemi where Besides, nothing beats the felings of building a car like that yourself instead of buying a new one off the dealer like a lot of other guys do, at least for me it does anyways