Yeah that is going to take a heck of an engine combo to make 600 hp from a SB Mopar with a hyd roller cam. I did a 427 inch SB a few years back with ported Edelbrock heads. We used a small hyd roller since it was a street driven road race car. The cam was 236@050 and it made 520 hp. That engine might have made 600 hp with a bigger solid roller but I don't think even the biggest hyd roller would have made 600 hp. Maybe it would've, we never bothered to test it.
These days there are better heads available than what we were using so if you have a really good cylinder head you might be able to get there. Good luck, I think it will take some time and money.
I'm shooting for as close as I can get not because I am dead set on a 600hp bragging right, but because I figure that's what it will take to get me down into the 10's in an all steel '70 Duster . I plan on using the trick flow 190's and sticking with traditional LA valvetrain elements.
If I have to go with a solid I may consider that too.
