First off- that Tornado thing is crap, throw it in the trash, or recycle it as a doorstop. If you are lucky, you can pass the misery on to someone else via eBay.
I am going to guesstimate at your potential HP numbers, but you really should get it on a dyno before you tinker with it, so you have a baseline, and can tell if your modifications are helping or hurting.
Those early 289's got about 200 SAE crank HP, so you are probably looking at about 160 to the ground if you have an auto, maybe 175 with a manual. Not a lot to start with.
Upping to the 4bbl intake, carb and K&N should get you 30-40 hp right away, and is probably the biggest gain you will see. You might get a few more from the exhaust, but don't expect huge numbers, 10-15 at most. The fact that you are combining intake and exhaust mods will help, but make sure those 40 year old internals can take the added strain!
Short answer: I will guess your rwhp will be in the 225-230 range. Let me know how close I got!