U bolt size

I'm adding two leaves to my stock spring pack for a cheap budget boost, and need to get new U bolts made. I have the 8.25 rear axle. has anyone done this and can give me some dimensions? I have read that the 8.25 axle needs 3" u bolts, but I measured and I saw that the width in between the threads was less that 3 inches on my XJ. I also found some 2 7/8th and 3 1/16th u bolts at the local parts stores, will they work? I also want to make sure that I get enough thread on the bolts as well.

Thanks

3" is correct for the 8.25 axle. As for the length you should probably measure cause it could make a big difference depending on your setup. I hear from 7-9" alot

after some searching, i think i'm going with 3 in. diamater and 9 inch length