Hi Barney -
For new parts, I find that almost without exception that the parts from the classic center are the best deal. Their shipping is extremely reasonable also. If you join the MBCCA you will get 15% off on parts also. The problem with the Classic Center (and MANY of the other providers) is that they will provide the "replaced by" part that doesn't really match on some items. (Example - forget about getting proper sun visor clips from the classic center, forget about getting the proper left and right fresh air vent levers if you have an early car, etc). They will send you a later part that is wrong for both of those.
Scott