I would say the spark problems are over, but new problems arise in a diesel conversion---i have been working on benz diesels for over 30 years, still drive the old ones, with the benz sometimes when #1 glowplug goes bad the glow system doesn't turn on(ignition problems), vacuum is used to shut off---had a lot of "can't shut my car off"---and with the 240 engine you had better match the motormounts to the engine, think the A ehgine can have vibrations you should drive a old benz diesel with cheap or bad motormounts---the windshield on my first 240D would rattle in the rubber with good mounts----and it's only 62hp, not hard to get with A engine not far from stock ----a 240 benz engine on stiff mounts can crack and shake off ----the 2.5 turbo diesel would be better, lighter, more powerful, less vibration
I also have Kubota lawnmower, actually 2, one split the block in 1/2 at 900 hours, the going strong at 4000 hours