You can pour a connecting rod bearing by the same procedure. However, I would remove the rod and use a piece of shafting same size as the throw part of the crankshaft for a mandrel. It will be easier to pour the rod bearing away from the engine. Remember to include some shims.
Babbitt metal is an alloy of 4 parts copper, 88 parts tin, and 8 parts antimony. You can use the babbitt from the old bearing plus a little more new or used babbitt.
To pour a split bearing, both upper and lower halves at the same pouring:
1. Align the shaft, square and centered.
2. Place cardboard liners between the two halves and against the shaft. Make holes in the cardboard near the shaft for the passage of the molten babbitt from the upper to the lower part. Pour thru the grease hole in the cap. The metal at the holes is easily broken when the cap is removed.
To form the ends of the bearing make cardboard washers and back them up with fire clay mixed with water. Be sure no water comes in contact with the melted babbitt. Even a few drops of water will cause the metal to spatter.
3. To prevent the babbitt lining from working loose, small holes may be drilled into the castings. The metal running into these holes secures the lining to the cap and lower casting.
4. To make removal easier, blacken the shaft with a candle flame.
5. Preheat the castings and the shaft. Otherwise, the metal may cool too quickly and not make a complete and smooth bearing.
6. The babbitt should be heated slowly until it will quickly burn a pine stick to a dark brown. (no flame). Too much heat will injure the metal. Too little heat, it will not pour well. A little crushed resin added to the babbitt just before pouring will produce a smoother surface.
7. The pouring must be continuous.
If the flanges on either end of the bearing are broken, you can make a collar from a cardboard tube or a blackened copper tube and place it between the engine frame and the cardboard washer before mentioned in step two. This will give space for the metal to flow around the ends and form the sides. The cardboard liners mentioned in step two should extend thru the collar to cast the sides in two halves.
8. To align the shaft make 'V' blocks of 2x4 wood. Place engine on solid level surface. Shim the 'V' blocks under the flywheels.
This procedure should produce a good smooth bearing without scraping. In your setup include some shims so that the bearing can be taken up when needed. Do not feel badly if on the first try you do not get a good bearing. Melt it down and try again.