Oh! I know have a guide before I did a single piece of math!
So you would have to add 6lbs. of weight for every cube over the likityand this guy is at 388 cubes?
Jeez, this guy basically did 85% of your homework for you. Awesome!
You could come under the weight with a 3.58 (360) strike crank into the 340 & at a .030 over bored cylinder be at 372/373 cubes.
OR
Stroke the 340 to over 400 cubes and weight in the trunk.