I would use rears up front. You can make your springs hold what you like because you are making the pack and they are cheap. In the future it you add weight like a winch, bumper, exo, ect... you can adjust your front springs by adding a leaf. If you want more flex you might want to look at the 51" toyota rears, these springs come off of 90-95 trucks. With 1tons and the weight of a 350 I don't think you will have problems with flex.
