The J shock will fit in the H yes but check the ride hieght and steering rake. The H swingarm is 20mm longer and the steering rake is the same as the J = 27.5- and I think from memory the J shock is about 8mm longer than the G/H shock so it does have a tendancy to sharpen up the steering, which is good in the G coz its rake is 30. That why I say it would be good to get a softer spring, and the initial compression would be a bit softer too.