The LT4 made 330 crank HP, not a big deal. It had better heads (about $1150 assembled, not worth it), better intake (raised runner for both), and a small cam. The LT4 HOTCAM was not the same as the standard LT4 cam.
Port your heads and run a better cam if you want power.
Yes, the 95 and up opti is much better, you need a timing cover, new Opti wiring harness (one setup of wires which plugs into the wiring harness), and vacuum lines to the TB ducting, which means new TB ducting or just cut your own holes with a punch. It basically has better sealing, and is rebuildable, otherwise it performs the same function.