My point here is that it is hard to determine what type of stresses an old bridge has been subjected to and the buck beams were never disigned to handle the shear applied as a pick point for the entire bridge. Just proceed with extra care on this type of pick. A good safe pick is worth the extra expense. Here are a few suggestions. We normally do not accept more than four-point lifting for a single crane lift.
Reason is, the inaccuracy in sling lengths can change the load pattern significantly.
From that point, it would be better if you lift by the main beams. If you are lifting by the secondary beams, the shear capacity of the joint at the main beam should be at least 1.5 times the theoretical shear. This accounts for sling length tolerance. If you have lifting beams, and the arrangement is statically determinate, the magnification is not required. For onshore lifts, a minimum dynamic load factor of 1.15 is provided, and lifting points and accessories are designed for a DLF of 1.5.