He states that they are for a 360. Bore size is 4.040".
Standard 360 bore is 4.000, so these being 4.040 would make them for a 40 over 360.
These would fit a standard bore 340 (being 4.040"), but I'm not sure what it would do to the compression without a little research. Being that the 340 & 360 use the same rod length, and deck height from crank centerline to head face, but have different stroke. This would indicate that they adjusted for the compression in the piston. You have to look at the dimension from the centerline of the wrist pin to the top of the piston dome (piston compression height) to determine how or if they would work in a 340. My initial thought is that the 360 pistons are shorter than the 340 (given the same compression and difference in stroke). This would mean that the 340's need a higher compression height on the piston to get the same compression as the 360. So these should have lower compression in a 340 than a 360. I can't tell you how much without digging into the books and doing some calculations.