Yeah, that really bites when you do everything right and still have troubles. I think Phat may be on the right track with the bearing side chamfer idea, expecially on the rods. I think the pan needs to come off before you run the engine any more to see what is happening. When you set up the old babbit rods, you removed shims from both sides until it took a light blow of an 8 oz. hammer to move the rod back and forth on the rod journal. Then you were supposed to add one .002 shim and you should be able to move the rod back and forth with one hand. (Pretty scientific methods, huh).
I am not sure about setting up insert rods like this, but still you should be able to move the rods back and forth on the crank. Also in the shop manual they show tightening the pin retaining bolt in a special piston vise because if you use a regular vise and clamp down on the rod, Chevrolet says you will twist the rod. I am going to get started on my 261 and will have to figure out some kind of 'piston vise'.
I don't know if I was any help, but be sure to post back with results when you find something. Also, welcome aboard!!!
