The 2.6 has a smaller bore. Stroke is the same as the 3.0. In fact the 2.6 and 3.0 have different block and head castings, with smaller ports and valves, but many internal parts are the same, and all the exterior dimensions are the same.

I wish the 2.6 DID just have a shorter stroke like a 327 Chevy versus a 350. Then it would be easier to increase the displacement to 3.0 by just changing the crankshaft and pistons.

Duke