I have to check the part numbers, but its just AE cone washers like used on the top plate and the bolts are 5/40 x 1/2 or 3/8 tapered head. Dremel down the nipples so its flush, then drill a hole for the bolt. Not sure what size bit I used but I think I used a #40 .0980. I drilled a tiny pilot hole first. No nut on the back.