Don't need a longer shock particularly, I've got 2 shocks, one needs serious servicing and the other has an incredible hulk 750lb spring in, a mate has a new 450lb 222mm for a very good price which would be much less than the cost of servicing the other and a new spring.....damn this suspension stuff is complicated
Edit the shock with the heavy spring is a Romic, typically no other springs seem to fit only Romic. Could be wrong though.
Oh and the 450lb Rmomic spring I got for a tenner posted from Pinkbike is far too long. Christ I'm an idiot, didn't even ask the size.