Depends entierly on how the springs have been wound.
On the majority of lift kits I've seen the longer ones go on the back, but not always. The springs scorpion supply with their are a good example where the front has very long progressive springs and the rear has shorter, stiffer springs.
Scorpion racing springs should have a code painted on one end (where it would sit against the spring seat) from this code scorpion should be able to tell you which way round they go. IF not then just fit them either way round and see if the 90 sits level, if not then just swap them round. Remeber to check they are the right way round before you refit the dampers etc. to make life easier if they are the wrong way round.
