340 #'s

Check on the driver side of the block kind of towards the rear. It should have a series of numbers and the last set of numbers should say 340, if not, I am afraid that you got a 318. You cannot bore a 318 out far enough to make a 340 and still have a depndable running motor in warm conditions. The water jackets are too close to the cyclinder walls to do that. It would run, but you would have a lot of cooling issues with it.

Chad