Hello,
You are better off with the 6.3. This is a complicated engine that will probably make you drive off a cliff if you ever need to get into it.
IIRC, the distributor cap is something like US$400
The M 100 V-8 will be much more reliable and is a conventional engine, iron block, alloy heads with ballstud rockers.
The M 189 six is an all alloy unit in this version with shrink fitted dry liners AND a 45 degrees angle at the headgasket joint plane, a strange screw/locknut rocker arrangement and a waterpump that you may not be able to find for the first week of ownership
Stick with a 280SE 4.5 if you are in the US, it is a bombproof lump that will run to a million miles and NO air springs.
