I am currently rebuilding my 99 explorer motor and am about to send my heads into the machine shop to get checked out. I have heard it's a good idea to get new valve springs and possibly roller rockers? What is everyones opinions on that? I am also looking for a good street/autocross CAM for the motor, hoping for 275-300hp. I've heard B303 or E303, but then I've also heard that they are really outdated. I'd rather not get custom because of budget concerns.