Nothing wrong with a 468! We had a 468 in the Vega when I got my comp. license the first time around back in the 90s. 13.5:1, aluminum heads, .722/.722 solid roller. It was a good running engine. In fact, it's the engine that was in the car when I put it on the rear bumper (see avatar).
This time around we wanted an engine that could grow (in cubic inches) if we wanted to go faster down the road, hence the current 565. At 980hp, this engine is still far from a "maximum effort" 565. It currently has 23* heads. 12* heads would make a minimum of 100 more horsepower and Big Chief heads would make even more power still. The cam is basically a mild (for an engine this size) solid roller that is easy on the valve train but still makes decent power. This is another area where we could make more power if we decided to later on. We can also increase bore size a bit more as well as stroke.
Yet another option would be nitrous. While our engine wasn't specifially built for nitrous, Reher-Morrison assured me it would easily handle a 200hp shot. If we decided to have it built for spray when we send it in to have it freshened, their nitrous 565 makes 1450hp while still using the same conventional BBC 23* Dart CNC 355cc heads, Edelbrock intake manifold (drilled and tapped for nitrous foggers) and 1150 Dominator. We could easily build our 565 to make more power than the Vega can currently handle.
For now though, I'm pretty content with nearly 1000 naturally aspirated horsepower.
We are going to be spending a good deal of time next year testing and getting the new combo sorted out. We are picking up in the neighborhood of 400hp and at least a second in ET and 20mph in trap speed so there will be a lot of tweaking and changes made to make sure the car is happy with the added power and most of all, safe.