Right, if I remember correctly, the 48 was a bored out 40... then the 52 was the 48 bore with a little more stroke... now same stroke but a little more bore.

Once by accident I put a connecting rod in from a 40 in a 52, didn't realize it until much later and tore it back down (always seemed to run fine)... then saw that the 40, 48, and 52 use the same rod, Doh! Never would have thought with the bore stroke changes that they would have been interchangeable.

Like I mentioned above, the 56a rod is larger diameter on both ends, and the bottom is bushed, the top is not.