I do not think 450hp for a 318 is a tall and hard order to fill. I do think the stock Edelbrock heads are up n need of some serious porting along with the intake and a nice 1-3/4 tube header into a well thought out exhaust system should be used.
Your camshaft, IMO, should not only be a little bit larger but you need to grab a more aggressive lobe with as much lift as you can use on the cylinder heads flowing abilities. Look to a good solid flat tappet. A solid roller would be easier to find the ramp rate but it is kind of pricey to purchase it and the supporting gear for it.
Do NOT be intimidated by the lack of cubic inches (perhaps a larger overbore?) but realize it will take more RPM to get to the goal. Something 3.55’s may not like and require a good custom stall converter.