I own a 92 300D 2.5 with 171k on it and have a few insights:

1. Timing Chain - If you aren't sure of the age of the chain, I would replace it. Measuring the stretch of the chain on the OM602 is a bit more involved than the OM617. I replaced mine at 150k, even though it was measuring less than 2deg of stretch.

2. Oil pump Chain - Asked my mech. about it and he'd never done one on one of these, so I ignored it.

3. Vacuum pump - Glad to hear that it was swapped out recently.

4. Belt Tensioner - make sure it is parallel with the plane of the serp. belt. If it's angled, replace it. Not a bad job - I did my vacuum pump, tensioner, and water pump all in one shot.

Other things to consider would be the condition of the radiator and thermostat. These engines run hotter than I thought they would and mine used to shoot up to 100C+ after running up a good hill. Once I replaced the rad and thermostat it never crosses 100C and settles back to 85C within a few minutes. I've been running Mobil 1 15w-50 (red cap) and have had good success. The oil pressure is much better with the 50 in it as opposed to the 0w-40 at least a half a bar at idle.

Hope this helps. I love mine.

Chris