Ah James, no, I disagree here.
Although I am sadly more into cosmetical details & differences on our cars than on the technical side (I am not a technical guy by education), these technical differences do draw my attention very much.
Furthermore, it is fun to have the different single engine pieces in your hands (pistons, crank, valves, gears, etc.) - especially during assembly. It is no fun, however, if you're tinkering around with broken parts like cylinder heads or so - this does not belong to my top 100. Anyway, as to the cams, there were only two cams produced for the M127 II (230 engine):
the early hollow version (A180 051 70 01)
and the late solid version (A180 051 84 01).
Both have the basically the identical cam dimensions and are regarded as "hot" cams.
This does (and did) not prevent shade tree mechanics from using any other sedan's cams as replacement - those do fit. Please refer also to
http://www.sl113.org/forums/index.php?topic=11908.0I am sure I had heard the "euro cam" idea before and always believed it true.
There's definitely no US versus Euro cam on the M127II.
This is, however, the case on the M130 engines (280 SE and SL).
That's why you might have been confused here.
As a recommendation to see what you have, take off your valve cover, get a little makeup mirror and hold it behind the rear end of the camshaft (it's tight there in the car). You should be able to read the number which is stamped in from behind and reflects the 7th and 8th digits in the spare part number of the cam, here: "70" or "84".
Since you have got a replacement engine you might already have the 84 01 camshaft.
Best,
Achim