Chevrolet did have a two groove balancer on the 235 engine starting about 1954 or 1955. Chevrolet offered power steering on the 1954 model. The second groove on the pulley was used for power steering or air conditioning. With a two groove balancer, one groove for the air conditioner, as shown in the preceeding post, and the second groove for power steering, the alternator can run off of the second groove of the air conditioner compressor, asuming you would use the Sanden-Sankyo compressor.
Fisher also makes a two groove aluminum billet balancer. It is a bit pricey, but does provide the two grooves.
