My car needed replacement U bolts and I had to buy a new bracket that goes on top of the cross member and that the hand crank fits through. I had to do some grinding on the new part to get it to fit correctly. I could not find the later U bolts.
In 30-31 the bolts are not "formed" (flattened) to fit the crank guide/spring retainer but exist almost as a "bent bolt."
The earlier crank guide/carrier is "squared" and has "landing places" for the flattened/squared bolt body. The later crank guide/carrier is "round" and presents half-round "seats" for the bolt body.
Either will work in the location - but you have to have the match between carrier and bolt.