The two barrel side draft carbs were used on many different cars, not just Datsuns. Find a supplier that can get rebuild kits and do it yourself. It is easy.
Or, find a shop that specializes in carburetors and be prepared to spend a considerable amount more to pay someone else to do the job.
The installation and tuning is where the skill comes in. Having a set of various sized jets, a tool to read the spark plugs helps. Even better is having an exhaust gas analyzer to get the carbs set and jetted correctly.
Get it too rich and it will consume excessive amounts of fuel, and wash the cylinders down, shortening the life of the cylinders and piston rigs, pollute the oil and risk bearing damage.
Get it too lean, and melt pistons.
Oh, and when the atmospheric pressure changes, you’ll need to check and change jetting.