Leaf spring slider mounting screws

Does anyone know the size of the mounting holes on the top of an Afro or speedway leafspring slider? I'm making a mount at work and forgot to bring a slider with me. Kind of thinking they are 3/8"??
Thanks

I thought everyone welded them in

IIRC they do have the holes like if one wanted to bolt them on but I think EVERYONE welds them.

I made some boxes to place the slider where the spring eye would be if the shackle was still there, most dont and just weld it ka ka to the frame rail.

All I used the holes for was too locate them, once I found where I wanted them the rails were notched and then they were welded in.

Dad had plates drilled and then bolted his in on the 72 Duster. It worked out well.
I can't swear to it but I think he also bolted them in on the 69 Dart.
I welded mine in...