The 7 1/4 is a smaller tube diam than the 8 1/4,8 3/4,9" and dana which are all 3". I have found some 7 1/4 plates that had the holes stretched to use on the 3" tubes axles.
Is it possible to use the 8 3/4, 3" u-bolts with the 7 1/4 shock plates and just pull them in then run them up tight with the nuts without elongating the holes?