Steering wheel bolt

When turning my wheel there is alot of slop before the steering actually engages. I thought it may have been the rack.NOT. I took the Grant wheel off and looked at the adpater plate to find that the plate sides that were convex to keep the adapter from spinning have been flattened out, so the entire center of the adapter is round. After taking the center bolt out I found that the threads of the bolt were either cross threaded or the bolt that I used was not the correct one.
Does anyone know the correct size (or possibly the part number) for the steering wheel bolt. I need to get another one so I can reinstall the wheel when the new adapter comes in.

If no one knows the size, does anyone have a service manual that might have the information in it. All I need to know is the correct size for the bolt. I think I may be able to run a tap through the column and repair the threads there, but I still need the correct bolt.