ALL A series timing cases are interchangeable, but they are not all the same.
The A10 & 1200 engines used a timing cover with a single timing indicator in the timing case & several timing marks on the pulley. From 1974 [I believe] the situation was reversed & the timing case was cast with the various timing marks cast into the case & a single mark in the pulley.

If you want to do a totally original resto on an A10 engine, then you will need to find a serviceable second hand A10 or 1200 timing case, but if you just want to restore it to service, then finding any good used 1974 & later timing case & matching pulley should not be a problem.

To fit it is a bit of a pain & is actually best done with the engine out of the car since it will be necessary to drop the oil pan to allow the timing case to come off & this pretty much destroys the sump gasket.

You will need a sump gasket for an A10 & 1200 engine [not the later 1974 & on A12 etc.] a timing case gasket, a water pump gasket, & a timing case seal. This assumes that you have an A10 or 1200 engine.

These earlier engines had a chain guide inside the timing case & it might be an idea to ensure that the one that you are going to use [if present] is serviceable. Also check the timing chain for wear as now would be the time to fit any replacement parts that might be needed.

Your local Nissan dealers parts counter should be able to supply the parts you need & if they are dead lazy & pretend that they no longer have the parts books, then come back here & we will supply you with relevant part numbers.
Also try the usual auto parts houses, they still list a lot of this stuff.

If it's just your water pump that's faulty, then try just about any auto parts house you can find. If they don't have one in stock, they should be able to get one in overnight. The standard pump is the same for all A series engines I believe, but just be aware that there are also some variations such as aircon model water pumps. As long as the pump is listed against your engine, you're in.
The Nissan dealer should be able to do the same.