I have been thinking of purchasing a new Superduty to replace my existing. I have looked through a lot of data and for 2011, I cannot find any physical difference between a F350SD and a F450SD other than the F450 has 2" larger rear brakes. The F450 comes std. with the 6.7 and 4:30ls. When I price both out equipped the exact same way (except with 3:73ls in the F350), the F450 cost about $3K more. For 2011 they both have the same frame, tires/wheels, and running gear. Anyone know what other differences there are to justify the $3K difference in price? My local dealer doesn't know and doesn't seem to interested in finding out.