first of all you cant get 70mm springs, saying that my housemate (tom5190) has 70mm springs but ive never seen them for sale anywhere, unless you get them custom made
also you havent stated what car you have..
vtr's and vts's are heavier than lower powered models so they have stiffer springs, so if you fit 60mm springs made for a 1.1 should lower a vtr/s lower than 60mm as they are heavier on the softer springs
also get 100 posts and go in the for sale section