Horace,
I believe you have two issues. First, the horshoe type clamps are only for holding the quad tip to the exhaust pipe (I recall yours were used to hold the tip to the frame bracket/insulator). Second, the band clamp is used to hold the tip to the frame backet/insulator. This clamp uses a sheet metal screw instead of a nut/bolt arrangement. Sadly, I have not found a correct size reproductin for this band clamp and have resorted to stretching a reproduction and then re-bending it.
For the top notch restoration, the band clamp was spot welded to the U-shaped bracket that went into the unsulator.
Regards,