Im working part time at Advance auto so I can get them relativly cheap. We carry the Manroe sens-a-trac shocks for the rear of the IRS cobras so I was thinking of going with that or we have the heavy duty Monroe gas-matic shocks made for the bird. I have the Eibach pro-kit springs on it now and was lookin to stiffen the rear up a bit more. Even though they're not the Bilsteins would the cobra sens-a-tracs be stiffer than any stock bird shock or would those heavy duty bird shocks be the way to go? Thanks.