Harland Sharp (www.harlandsharp.com) makes a bolt on roller rocker P/N SV4004. Any GM style rocker will require guide plates, aftermarket studs, and the machining I described above on the heads you have.
Don't worry about EGR unless you have to pass emissions and they do a visual check. I've got one of the Offy dual ports, but I've never run it (bought it for $50 at a swap meet). I've heard mixed reviews on them.
Big tube headers will hurt your bottom end a bit. If you're rock crawling or trail riding, stick to 1 5/8" tubes to get a little more torque.
If you have the extra cash, do a port/polish on the heads along with your other mods. It really woke up my 360.
Bob
tufcj