Does anyone know what the input shaft diameter is, of the steering rack, on a Pontiac Grand Prix GT 3800 Series 3? I'm looking at two steering racks from NAPA. The NRP 221025 has an 11/16" input shaft, and the NRP 221023 has a 5/8" input shaft. I want to have the right one ready to go in as soon as I remove the old one. Thanks.