[Buford T. JuSStice]

I'm sure it has been said, but the open valley doesn't have to necessarily be a huge disadvantage. When you're building your block, right at the very beginning you can reduce the chances for failure significantly by shaving down the casting flash yourself, and getting rid of as many sharp edges around the area as possible. Make sure to clean up the area very very thoroughly before going any further. It may even be a good idea to do this before bringing the block to a professional machine shop, and if you aren't confident in your abilities, they would be happy to take your money and do it for you. I'm sure if you're still afraid of things falling down into the valley area, you can have mesh inserts inserted similarly to how you can put a mesh insert into the corners of a SBC's valley area. Make sure to use an very tough, inflexible, finely woven stainless steel mesh, and epoxy it in place, making sure NOT to place it anywhere that it would be in the way of other moving parts!