I had a late 05 6sp and I can tell you it got better mileage in town than it did on the interstate because of the way the trans is geared.
you will notice more power with the 06 for sure.

70 duster full chassis super pro 416 CNC Indybrock heads 727 w/brake

best so far 1.212 60 6.219 in 1/8 at 110.88 9.768 at 137.81 1/4