leaky heat riser

I have a right side stock exhaust manifold for a '70 340 engine that has the heat riser valve. Problem is the shaft on the valve has quite a bit of play in it and there is an exhaust leak. Can these valves have the bushing replaced or should they just be removed and a small freeze style plug be installed? Would like to keep the valve, even though not totally necessary since it rarely gets that cold here in so. Arizona, so start ups are not all that difficult in cold weather. Thanks, Ben.