D6C 47J sleeve metering injection pump

Hello,
i'am in France and a friend has a cat d6C 47J4723 (dates back to 1971 i think, with 140 FWHP, il was made in Scotland, and is i think the equivalent of  99J01551, 10K05984, 46J00664,  26K00794, 69J01984, and 24U00246 series in other countries) with a sleeve metering injection pump.
A week ago, the engine didn't want to start and it appeared that one plunger of the fuel injection pump (see the picture) was brocken. This engine wasn't use for many years and the diesel inside was really dirty. That is probably why the plunger broke.
Now he plans to find the 8S2243 wrench to take the rest of the pump off and replace it by a new one. Some people says it would be more safe to change the 6 pumps to avoid any problem... Of course, it would be more logical but i would like to know if anyone have face such a situation ?
Thanks
Alexis

i would have it rebuilt by a suitable injection shop. and drain all the fuel from the machine completely. then change the filters after steam cleaning the tank and flushing all the fuel lines. refill with clean fuel after reinstalling the pump. it would be an idea to have the injectors serviced too. eliminate them as a problem. if bad fuel damaged the pump the injectors are probably damaged too.

Yes, i forgot to mention that he drained all the fuell system and steam cleaned the tank ! As to find a suitable injection shop, it's not that easy in France. It seems that no one know this injection pump ! Only the cat dealer would do that, but it would be very expensive. You're right to mention the injectors, they probably need some replacement. I'll tell my friend to check that point too.  Thanks

im fairly positive there would be service manuals covering the sleeve type and any injection tech worth thier fees should be able to work on in it using the manuals