I've played around with leaf springs on my sandman trailer recently.....one tonner springs are much heavier and have a curvier profile. It left my trailer sitting really high. Like 4inches from top of the tyre to the wheel arch. i got normal van springs and it made a dramatic difference. I dont like the idea of lowering blocks, and i think in most states theyre actually illegal. You'd be much safer in getting van springs reset to suit the stance you want your van to have. Im sure a few guys here have done that already and might be able to help you out with a rough price of what it cost them