The engine is based on a 1986-1991 560SEL engine, but it's 10:1 pistons, lumpy cams, the 1981-1985 CIS style injection and ignition, some other stuff going on. (car started life as a 1985 380SE)

According to my service manual if you can push the lifter down by hand that means you have to replace it.

I do think the 560s had a crank sensor, but mine doesn't.