every long travel arm will require a different shock length. Teixeira Tech for example will require 21 5/8" shock. (gotta check my notes to be sure) other brands require 19" through 21". the shocks you have now may not be the correct length for the arms you buy. you should check your shock length then buy arms that require the same length shock.
just a heads up. id hate for you to spend all kinds of money only to find out your set parts don't work together.