I have been making the the square hole version of the leaf spring band clamps for 30 years now. I have sold over 10,000 sets and counting. Jim Cowels was making a round hole version (I think Jesse still is ). Any square hole sets Jim had came from Me. Ford leaf springs of the mid 60's to early 70's had at least 4 different versions of the band clamp hole. The 4 versions I have seen used, Round, Square, Square with a notch and D shaped. Most common for 65-67 Shelby's are the round hole clamps. Most common for 68-70 Shelby's are the square hole version. I have seen all 4 versions used on all years of Mustangs from 65-70. Yes I have a vested interest, but IMHO it's not worth trying to save the old ones, that's why I made them to start with. Also all of the components of mine are 100% made in the USA.
Rodney