What size are you looking for? I would think that with all the sizes Stengel Bros list that something should fit. If they are too long, just cut them off. GM probably listed close to 100 part numbers for U-Bolts in their master catalog of the period. Dealers never stocked many. Everyone that I have known either ordered them from the aftermarket like Stengel Bros. or had them made. I think buying from Stengel Bros. is a lot cheaper these days than having them made.
Trailers used to use square bend U-Bolts. Probably 40 years ago the round bend U-bolts became more popular because they stretch a lot less than the square-bend U-Bolts. Back when I started trucking over 50 years ago, we were constantly tightening U-Bolts, replacing broken leaves as well as broken U-Bolts. I'm glad those days are long gone. I have 9 dry fans on spring ride that all use the round bend U-Bolts and they are maintenance free. Everything else is on air ride, and air bags do blow out.
