The lag screws are 3/8″ x 1 1/2″ and the bunks should be able to loosen with a tap on the bunk. They hold pretty good, though if yours need replacing they probably have some dry rot and should be easy. The bolts probably will come out easy without other means than a wrench or socket. When you go to replace we trim the boards down to fit and taper the front with a chamfer on the rear. You may need to really pull the noses of the center bunks in hard. Lots of tension on the long bunks.
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