Well, I threw out numbers that I think will be close on the 273, 340 and 360. I'm hoping the others will chime in and let me know their thoughts. Maybe .5 isn't enough for the 340? If you bore a 318 out .030 you get docked .4, so maybe a .5 isn't enough?? After all, 318's are noth'n, and everyone is told to get a 340 or 360... maybe there should be more of a difference ?? LOL