I think I'd replace those grates, they look to be flaking pretty deeply so cleaning them after cooking could be more difficult, even after removal of the rust and seasoning the grates again.
I rebuilt one just like it a couple of summers ago. The parts are all still readily available, the only hiccup I found was that I needed to get a fitting adapter for the new regulator. The old "quick connect" regulator used a different size fitting than the newer ones that are used with OPD tanks.
I second the recommendation to go stainless with the flavorizer bars, there is a guy on e-bay who sells a heavier gage version that are priced comparably to the Weber version as well. The burners don't look too bad so if they're working well and not corroded you can probably keep them going for a while. I found the burners didn't need replacement as often as other parts.
When I rebuilt mine, I went with PCI grates and they made for some fantastic grill marks, I was concerned about the porcelain eventually flaking off though so if I had to do it over again, I'd go with the stainless rod grates for their ease of cleanup, they don't retain heat quite as well as the PCI but they're pretty worry free.
Congratulations on your find, I'm sure it will still be going many years from now