[camgrinder]

If the crankshaft has been reground the plugs have to be removed and the oil lines cleaned. Then you can install new plugs. Most people who do this type of work make the plugs themselves. If the engine had a rough life, with lots of carbon build up or a mechanical failure that sent metal thru the engine, I would R&R the plugs.
Some people might tell you to take a pipe cleaning brush and some carb cleaner to the crank without removing the plugs. This may not remove all the junk at the end of the oil line.