They will definitely help! L/T's should be awesome! Wish I'd gone that direction with mine - bought a Bassani catted x before I thought about headers. Now I have FRPP JetHot coated shorties in the garage that I'll be installing over the holidays. Can't wait!
Good luck on the suspension - you'll definitely notice a difference!
I did the same. I bought a bbk x-pipe for stock shorties, but I have heard so many good things about L/T's that I just got to do it. Of course the install is a crock.