Cap61, the cast crank is plenty strong enough for normal high performance use, the can take a lot of punishment. I have a few friends who regularly drag race cars with cast cranks, and have no problems at all. The 063 heads are a great head for a street performance car, they're small oval port, closed chamber heads. About 101cc chambers, should have pretty good compression ratio with those heads. They flow great with the stock valves even. Use them!!!