Girdles for Big Blocks in my opinion are just Band-aids. The things that have helped me are Aluminum main caps and ARP studs everywhere. I have had great luck with BCR caps, I know they sell a girdle as well that ties it all together but I have no experience with them.

I don't know that that combo will make 650HP but it should make good power.

Be careful if you start getting close to 700Hp this is what will happen: