Based on the additional information I don't think removing the converters will gain you anything. Whatever fuel quality issues exist are not likely to harm the converters as long as the fuel does not have significant TEL content. If there is a problem with dirt or particle contamination, you might consider replacing the fuel filter more frequently than recommended. The KE system has a lot of precision machined hydraulic components, and they don't take kindly to dirt. Stalling or hard starting could be a vapor pressure problem or water contamination. If water is a problem consider installing some kind of water trap. Most diesels have them.
Sounds like your biggest problem is going to be finding a commercial shop that can do proper repairs when needed.
There are still a bunch of fifties vintage American cars running around in Cuba. Lords knows how they keep them running, but necessity is the mother of invention.