A not very uncommon problem is that some 3000 blocks, after being restored, develops an internal leak between the oil and water galleries. This results in the coolant becoming contaminated with oil.
There is a kit for sale in the UK that is supposed to fix this problem. It consists of two ground pipes and a drill kit. You are instructed to drill two of the oil galleries and then the pipes should be pressed into these enlarged galleries. Unfortunately the drills that are supplied are of a larger diameter than the supplied pipes, making a press fit impossible. In the following images you can see a much better solution that actually works. I drill and tap both galleries and then make two threaded pipes in suitable dimensions. These pipes are screwed into the block together with a liberal amount of thread sealant. I would like to thank Cees Cardol in the Netherlands for pointing me in the right direction and to Lars Törnblad in Sweden for helping me with the fabrication of the tools needed for this complex operation.