It's all about compression, especially if you reside in California, where premium is only 91. I have a 572 Indy Head Max Wedge 750 HP and 775 lbs. of torque. It's 10.5.1 and runs great on California premium. Fuel is fed through an EZ FAST 2.0 system with eight injectors. It's a solid lifter setup that was built for drag racing, although, it will never see a racetrack... I'm 78 and don't trust my reaction time the way I used to. If you, or anyone else reading this, were to go with aluminum Indy heads, you'll have to go with TTI headers because of the angled spark plug holes. I know there has been a lot of pros and cons regarding Indy Head engines; however, I have to say my engine always runs great, never over-heats and feels like it wants to through you out the back window with just a little throttle!!
Good luck with whatever you end up with. Also, one really nice thing with our Road Runners... you can stick a huge engine in the engine bay and still have a lot of room for other add-on goodies.