Ok guys, here's the deal. You may be able to get away with reusing u-bolts, but it is not recommended if you want to do a quality job.
I worked in an engine factory for one of the big three. We had some bolts that we torqued to yeild (stretched) each time that they were tightened. We tracked these bolts so as not to use them more than three times. After that, we threw them away, even though they had good pistons and rods attached.
Fastener Engineering only allowed us 5 cycles for torquing the bolts period. We were able to use three and save two for service. This was no sales pitch, it was mandated by OUR OWN FASTENER ENGINEERING DEPARTMENT who was responsible for determining the torque for each fastener/joint on the whole vehicle.
When the bolts are torqued to yield, they have a permanent stretch for each cycle that they are torqued. I have measured this on the bolts when I set up the machines to torque them. After so many cycles, they will "neck down" where they were yielded and that will become the stress point where they will eventually fatigue and break.
So if you want to reuse bolts in a high stress application, it is your call. In some cases you can get away with it if they were only torqued once before. But if it was MY car and I was putting it together, I would replace the bolts with new ones. It is not worth a measly $30 for new u-bolts for me not to replace them and potentially have my axle fall off when my car is going down the street. Then you have to gather up your parts and call a tow truck and wait to get a ride home and then fix all the colateral damage from the axle falling off. Your call... Do you want to do it CHEAP or RIGHT???
Also, adding any other lubricants to the nuts and bolts can throw off the torque to clamp load that was used to put the parts together. Fastener Engineering test the nuts and bolts to be used as they are shipped in from the supplier with the coatings that were specified on the bolt/nut blueprint. Adding extra lubricant will affect the torque needed to reach the proper clamp load that was determined by Fastener Engineering. The excess lube will cause you to overtorque the bolts and put excess load on the fastener (bolt) where it will fatigue and break faster.
Mancini carries two types of u-bolts. One with knurling on the inner radius (to help clamp them and keep them from "creeping") and ones without the knurling.
