-fad/all,
As to the "extra cooling/passages" of the '92 vs. '93 & later cars-the earlier motor were of a closed-deck design, meaning when you pull a cylinder head off you cannot see between the cylinders on a closed deck motor. However, the closed deck blocks did have coolant passages between the cylinders, but block material was left remaining between the cylinders up near where the block meets the head for strength. Thing is, for every closed deck block that came out of the casting & cylinder lining/siliconizing (sp?) process properly, some 10+ were thrown away as inferior...very expensive block with those numbers(MBZ musta lost their A$$ on early 500Es, 500SLs & 500 SELs). Plus, that extra material, in an under-stressed 320ish HP road car application, was overkill. Remember, these motors were meant to develop 1,000+ twin turbocharged fury, and to do so dependably, in endurance races. Later, MBZ figured out how to minimize their production losses and went to the open-deck design, which proved more than adequate to the task but saved them dinero. This is why the tuners will only bore out a closed-deck motor-with the later blocks, there wouldn't be enough material up near the head gasket to seal the cylinders properly.
Ultimately, unless you plan to 6.0 the car, I'd go for whichever aesthetically appeals to you...subjectively, those 7 extra HP are truly negligible, for one; the bigger brakes of the later cars are only viable if you track the car, or live in the land of the autostrada/autobahn/autoroute (I track my car, so popped on the later brakes). The later stereo is quite a bit better than the early ones (I replaced mine completely).
And I do like that clamshell arm rest - on my upgrade list
