I would guess that you would get another 40 hp more with the 347 kit and the Holley package.
The Holley kit will work with a 347 stroker kit.
There are a lot better heads out there that will make more power than the Holley heads. Look in Summit magazine. They have a Trick Flow package similar to the Holley one. It will make way more power.
Or, you could buy some AFR heads and pick your own intake and cam combo to go with them. This might be the way that you can make the most power and still be street able.