that looks pretty bad, I would just buy a new one (timing cover), you can get them off ebay or direct from japan, 75$ + shipping. I routinely replace water pumps now every 10k, its the one area of the Z that has gotten me going back 30 yrs. I had one break a the shaft and take out the radiator, another just spring a leak, stranding me for hours until I did a replacement away from home. Now I just replace it with one of the cast impeller types if I can feel ANY radial movement. Don't over tighten the bolts, use some anti seize.
While you have the timing cover off replace the timing chain and guides and tensioner, or at least the guides. I just recently had the tight side guide just break loose and fall down into the bottom of the cover. Not sure why, as the chain did not seem worn. I did the whole job with the engine in and the hood on. Not that bad.