First, I would check with the engine builders on this site about boring the Genesis block to 527. I haven't heard of a member here boring that big with a Genesis or Pond block. The only block that I've heard going that big is the big bore Shelby block.
Second, the Pond aluminum block will save you about 125 lbs over an OEM FE. The Shelby block will save you about 100 lbs over an OEM FE block. I believe I'm reasonably close on those figures, but double check me.
Third, while Barry R loves to use the Genesis block, from what I've read, many others have run into problems with them. On the other hand, "xl8or", Scott, used the Genesis block and seemed to have no problems at all.
Fourth, the Genesis block is about $1,000 less than the Pond block and about $1,600 less than the CSX block. So, upgrading to aluminum is not cheap, but then removing 100-125 +/- pounds and increasing the resale value of the car are two advantages of the aluminum block.
Fifth, an aluminum block makes it easier to spot leaks.
