The ears on the block to mount the motor mounts are different on the left side from 273/318 to the 340/360. You will have to get a 340/360 mount for the left side. The right side mount will bolt up on all sb engines.
This is true, but good luck with the 360/340 mount. They are no longer produced, just the 318 mounts. Fortunately, all you need is a small spacer to make the 318 mount work on a 340/360.