I don't totally agree..... on the M103 engines original thermostat housing was crummy plastic, replacement part is a metal alloy. Original radiator outlets would snap like fresh saltine crackers, replacement has metal sleeves.
Just a few examples of improvement, but I agree that it is a bummer to have to pay for those parts when it was a design flaw to begin with.
'07 R320 CDI " Manta Ray"
'62 300d Adenauer-350 Chevy
'12 VW Passat TDI 6/speed
'03 Dodge Ram 3500 - "Clifford, the big red Dodge" - Cummins w/6-speed
'68 Mustang fastback