Hi Richard, I would apply penetrating oil to the nuts and then using a chisel clear out a small area by each bolt top. Clamp vise grips tightly to the tops of the bolts and use a "johnson bar" to increase leverage on turning the nuts. If you can't remove the nuts that way I would remove some more wood by the head of the bolts and hacksaw them off. Once removed I would use new hardware and fiberglass handles.