One thing about the LD 512. The 1.54 rod ratio adds more thrust on the cylinder wall. I would make sure you have the block sonic tested and find a good one. No need to be worried about a short comp height. OEM engines now are all close to 1" comp height and go 200,000 miles. In your light car with the heads you have I would do a 470. Quicker rpms and your heads will support 470 cubes well.