I have tried to move it around so I could get it as close to the frame as possible, but this is the best I could get it. I am not saticfied with this result, so I have not drill the holes in the frame yet. Am I wrong or should it be like this??
It should probably be a little tighter, unfortunately tolerances in the 60's were pretty big. Are these the factory frame rails? If you center the crossmember, how much gap is there on each side?