Interesting.... With a 4.46 bore-center-to-bore-center distance, that would leave .240 inches or less for sleeve walls and coolant gap. That would take out the cast bore walls for all practical purposes; they would be gone, or what might be left would just crumble and break out, and leave the sleeves supported at top and bottom only. I would imagine they would have to be welded top & bottom to seal off the water jacket, and/or have the cooling jacket filled. And with a max wall thickness of under .120" each.....not counting any interference with the valley or outside block surfaces. Sounds like a challenging proposition....but knowing hot-rodders, it may well have been done!