The block ears are either closer together or farther apart (I forget which) on one side (forgot that too) of the 318 block compared to a 360 block so if your mts are narrower than the block ears then washers/flat spacers works well. the other way if the mt is wider than the ears you'd need the other mt. If a prob on the bottom (kmember) end is the mt being bolted behind the block ears?