Doing my first rear end swap.

I'm pretty sure you will need new U bolts and shock mounts. You can verify that by measuring the tube diameter of the 7-1/4 vs. the 8-1/4. Pretty sure the 7-1/4 is 2-1/2" tube and the 8-1/4 and 8-3/4 rears are 3" tubes. Some guys say they make the shock mounts work by grinding out the holes so a 3" U bolt will fit. Haven't looked into doing tht myself.