if removing the risers makes the block sit level and there is sufficient clearance elsewhere (radiator hoses) then remove the risers. Are the water outlets on the bottom of the block original to the vehicle? There are a couple of different styles of these that would also lower the block 33-34, 35. There should be an oil return tube at the rear main cap that assist the oil into the pan and away from the rear pan gaskets, when the engine is at angle, this also helps in preventing leaks.