What are you going to put this engine in?

500HP is real "do-able" with a big block - but being able to use the HP is another issue. That cam could be problems for a street applications. You'll definitely have a rough idle and you'll probably need 2800 - 3000 stall speed with an automatic (with 3.90+/- rearend) Do you really want a mechanical valve train?

Give us some more particulars and I'm sure we'll be able to help you out. Pat is the BB master - listen very closely to anything he posts in reference to BB builds. He's forgotten more than most of us will ever know about building serious streetable and racing HP!

Regards,
Glenn