Getting back on the original question, our rules are similar regarding the axle slots stating "The built-in axle slots in the block must be used and cannot be modified." However, don't you modify the axle slots the moment you put the axles in them. My thought was to just sand/shave down the bottom of the block and use a jig to drill canted holes above the slots (same wheelbase, just higher up on the block) before cutting the block to the shape of the car. If needed I can deepen the slots to my canted holes.